The C API code is distributed with MySQL. It is included in the
mysqlclient library and allows C programs to
access a database.
Many of the clients in the MySQL source distribution are written
in C. If you are looking for examples that demonstrate how to use
the C API, take a look at these clients. You can find these in the
clients directory in the MySQL source
distribution.
Most of the other client APIs (all except Connector/J and
Connector/NET) use the mysqlclient library to
communicate with the MySQL server. This means that, for example,
you can take advantage of many of the same environment variables
that are used by other client programs, because they are
referenced from the library. See
Chapter 8, Client and Utility Programs, for a list of these
variables.
The client has a maximum communication buffer size. The size of the buffer that is allocated initially (16KB) is automatically increased up to the maximum size (the maximum is 16MB). Because buffer sizes are increased only as demand warrants, simply increasing the default maximum limit does not in itself cause more resources to be used. This size check is mostly a check for erroneous statements and communication packets.
The communication buffer must be large enough to contain a single
SQL statement (for client-to-server traffic) and one row of
returned data (for server-to-client traffic). Each thread's
communication buffer is dynamically enlarged to handle any query
or row up to the maximum limit. For example, if you have
BLOB values that contain up to 16MB of data,
you must have a communication buffer limit of at least 16MB (in
both server and client). The client's default maximum is 16MB, but
the default maximum in the server is 1MB. You can increase this by
changing the value of the max_allowed_packet
parameter when the server is started. See
Section 7.5.2, “Tuning Server Parameters”.
The MySQL server shrinks each communication buffer to
net_buffer_length bytes after each query. For
clients, the size of the buffer associated with a connection is
not decreased until the connection is closed, at which time client
memory is reclaimed.
For programming with threads, see Section 22.2.15, “How to Make a Threaded Client”. For creating a standalone application which includes the "server" and "client" in the same program (and does not communicate with an external MySQL server), see Section 22.1, “libmysqld, the Embedded MySQL Server Library”.
This structure represents a handle to one database
connection. It is used for almost all MySQL functions. You
should not try to make a copy of a MYSQL
structure. There is no guarantee that such a copy will be
usable.
This structure represents the result of a query that returns
rows (SELECT, SHOW,
DESCRIBE, EXPLAIN).
The information returned from a query is called the
result set in the remainder of this
section.
This is a type-safe representation of one row of data. It is
currently implemented as an array of counted byte strings.
(You cannot treat these as null-terminated strings if field
values may contain binary data, because such values may
contain null bytes internally.) Rows are obtained by calling
mysql_fetch_row().
This structure contains information about a field, such as
the field's name, type, and size. Its members are described
in more detail here. You may obtain the
MYSQL_FIELD structures for each field by
calling mysql_fetch_field() repeatedly.
Field values are not part of this structure; they are
contained in a MYSQL_ROW structure.
This is a type-safe representation of an offset into a MySQL
field list. (Used by mysql_field_seek().)
Offsets are field numbers within a row, beginning at zero.
The type used for the number of rows and for
mysql_affected_rows(),
mysql_num_rows(), and
mysql_insert_id(). This type provides a
range of 0 to 1.84e19.
On some systems, attempting to print a value of type
my_ulonglong does not work. To print such
a value, convert it to unsigned long and
use a %lu print format. Example:
printf ("Number of rows: %lu\n", (unsigned long) mysql_num_rows(result));
The MYSQL_FIELD structure contains the
members listed here:
char * name
The name of the field, as a null-terminated string. If the
field was given an alias with an AS
clause, the value of name is the alias.
char * org_name
The name of the field, as a null-terminated string. Aliases are ignored.
char * table
The name of the table containing this field, if it isn't a
calculated field. For calculated fields, the
table value is an empty string. If the
table was given an alias with an AS
clause, the value of table is the alias.
char * org_table
The name of the table, as a null-terminated string. Aliases are ignored.
char * db
The name of the database that the field comes from, as a
null-terminated string. If the field is a calculated field,
db is an empty string.
char * catalog
The catalog name. This value is always
"def".
char * def
The default value of this field, as a null-terminated
string. This is set only if you use
mysql_list_fields().
unsigned long length
The width of the field, as specified in the table definition.
unsigned long max_length
The maximum width of the field for the result set (the
length of the longest field value for the rows actually in
the result set). If you use
mysql_store_result() or
mysql_list_fields(), this contains the
maximum length for the field. If you use
mysql_use_result(), the value of this
variable is zero.
unsigned int name_length
The length of name.
unsigned int org_name_length
The length of org_name.
unsigned int table_length
The length of table.
unsigned int org_table_length
The length of org_table.
unsigned int db_length
The length of db.
unsigned int catalog_length
The length of catalog.
unsigned int def_length
The length of def.
unsigned int flags
Different bit-flags for the field. The
flags value may have zero or more of the
following bits set:
| Flag Value | Flag Description |
NOT_NULL_FLAG | Field can't be NULL |
PRI_KEY_FLAG | Field is part of a primary key |
UNIQUE_KEY_FLAG | Field is part of a unique key |
MULTIPLE_KEY_FLAG | Field is part of a non-unique key |
UNSIGNED_FLAG | Field has the UNSIGNED attribute |
ZEROFILL_FLAG | Field has the ZEROFILL attribute |
BINARY_FLAG | Field has the BINARY attribute |
AUTO_INCREMENT_FLAG | Field has the AUTO_INCREMENT attribute |
ENUM_FLAG | Field is an ENUM (deprecated) |
SET_FLAG | Field is a SET (deprecated) |
BLOB_FLAG | Field is a BLOB or TEXT
(deprecated) |
TIMESTAMP_FLAG | Field is a TIMESTAMP (deprecated) |
Use of the BLOB_FLAG,
ENUM_FLAG, SET_FLAG,
and TIMESTAMP_FLAG flags is deprecated
because they indicate the type of a field rather than an
attribute of its type. It is preferable to test
field->type against
MYSQL_TYPE_BLOB,
MYSQL_TYPE_ENUM,
MYSQL_TYPE_SET, or
MYSQL_TYPE_TIMESTAMP instead.
The following example illustrates a typical use of the
flags value:
if (field->flags & NOT_NULL_FLAG)
printf("Field can't be null\n");
You may use the following convenience macros to determine
the boolean status of the flags value:
| Flag Status | Description |
IS_NOT_NULL(flags) | True if this field is defined as NOT NULL |
IS_PRI_KEY(flags) | True if this field is a primary key |
IS_BLOB(flags) | True if this field is a BLOB or
TEXT (deprecated; test
field->type instead) |
unsigned int decimals
The number of decimals for numeric fields.
unsigned int charsetnr
The character set number for the field.
enum enum_field_types type
The type of the field. The type value may
be one of the MYSQL_TYPE_ symbols shown
in the following table.
| Type Value | Type Description |
MYSQL_TYPE_TINY | TINYINT field |
MYSQL_TYPE_SHORT | SMALLINT field |
MYSQL_TYPE_LONG | INTEGER field |
MYSQL_TYPE_INT24 | MEDIUMINT field |
MYSQL_TYPE_LONGLONG | BIGINT field |
MYSQL_TYPE_DECIMAL | DECIMAL or NUMERIC field |
MYSQL_TYPE_NEWDECIMAL | Precision math DECIMAL or NUMERIC
field (MySQL 5.0.3 and up) |
MYSQL_TYPE_FLOAT | FLOAT field |
MYSQL_TYPE_DOUBLE | DOUBLE or REAL field |
MYSQL_TYPE_BIT | BIT field (MySQL 5.0.3 and up) |
MYSQL_TYPE_TIMESTAMP | TIMESTAMP field |
MYSQL_TYPE_DATE | DATE field |
MYSQL_TYPE_TIME | TIME field |
MYSQL_TYPE_DATETIME | DATETIME field |
MYSQL_TYPE_YEAR | YEAR field |
MYSQL_TYPE_STRING | CHAR or BINARY field |
MYSQL_TYPE_VAR_STRING | VARCHAR or VARBINARY field |
MYSQL_TYPE_BLOB | BLOB or TEXT field (use
max_length to determine the
maximum length) |
MYSQL_TYPE_SET | SET field |
MYSQL_TYPE_ENUM | ENUM field |
MYSQL_TYPE_GEOMETRY | Spatial field |
MYSQL_TYPE_NULL | NULL-type field |
MYSQL_TYPE_CHAR | Deprecated; use MYSQL_TYPE_TINY instead |
You can use the IS_NUM() macro to test
whether a field has a numeric type. Pass the
type value to IS_NUM()
and it evaluates to TRUE if the field is numeric:
if (IS_NUM(field->type))
printf("Field is numeric\n");
To distinguish between binary and non-binary data for string
data types, check whether the charsetnr
value is 63. If so, the character set is
binary, which indicates binary rather
than non-binary data. This is how to distinguish between
BINARY and CHAR,
VARBINARY and VARCHAR,
and BLOB and TEXT.
The functions available in the C API are summarized here and described in greater detail in a later section. See Section 22.2.3, “C API Function Descriptions”.
| Function | Description |
| mysql_affected_rows() | Returns the number of rows changed/deleted/inserted by the last
UPDATE, DELETE, or
INSERT query. |
| mysql_autocommit() | Toggles autocommit mode on/off. |
| mysql_change_user() | Changes user and database on an open connection. |
| mysql_close() | Closes a server connection. |
| mysql_commit() | Commits the transaction. |
| mysql_connect() | Connects to a MySQL server. This function is deprecated; use
mysql_real_connect() instead. |
| mysql_create_db() | Creates a database. This function is deprecated; use the SQL statement
CREATE DATABASE instead. |
| mysql_data_seek() | Seeks to an arbitrary row number in a query result set. |
| mysql_debug() | Does a DBUG_PUSH with the given string. |
| mysql_drop_db() | Drops a database. This function is deprecated; use the SQL statement
DROP DATABASE instead. |
| mysql_dump_debug_info() | Makes the server write debug information to the log. |
| mysql_eof() | Determines whether the last row of a result set has been read. This
function is deprecated; mysql_errno()
or mysql_error() may be used instead. |
| mysql_errno() | Returns the error number for the most recently invoked MySQL function. |
| mysql_error() | Returns the error message for the most recently invoked MySQL function. |
| mysql_escape_string() | Escapes special characters in a string for use in an SQL statement. |
| mysql_fetch_field() | Returns the type of the next table field. |
| mysql_fetch_field_direct() | Returns the type of a table field, given a field number. |
| mysql_fetch_fields() | Returns an array of all field structures. |
| mysql_fetch_lengths() | Returns the lengths of all columns in the current row. |
| mysql_fetch_row() | Fetches the next row from the result set. |
| mysql_field_seek() | Puts the column cursor on a specified column. |
| mysql_field_count() | Returns the number of result columns for the most recent statement. |
| mysql_field_tell() | Returns the position of the field cursor used for the last
mysql_fetch_field(). |
| mysql_free_result() | Frees memory used by a result set. |
| mysql_get_client_info() | Returns client version information as a string. |
| mysql_get_client_version() | Returns client version information as an integer. |
| mysql_get_host_info() | Returns a string describing the connection. |
| mysql_get_server_version() | Returns version number of server as an integer. |
| mysql_get_proto_info() | Returns the protocol version used by the connection. |
| mysql_get_server_info() | Returns the server version number. |
| mysql_info() | Returns information about the most recently executed query. |
| mysql_init() | Gets or initializes a MYSQL structure. |
| mysql_insert_id() | Returns the ID generated for an AUTO_INCREMENT column
by the previous query. |
| mysql_kill() | Kills a given thread. |
| mysql_library_end() | Finalize MySQL C API library. |
| mysql_library_init() | Initialize MySQL C API library. |
| mysql_list_dbs() | Returns database names matching a simple regular expression. |
| mysql_list_fields() | Returns field names matching a simple regular expression. |
| mysql_list_processes() | Returns a list of the current server threads. |
| mysql_list_tables() | Returns table names matching a simple regular expression. |
| mysql_more_results() | Checks whether any more results exist. |
| mysql_next_result() | Returns/initiates the next result in multiple-statement executions. |
| mysql_num_fields() | Returns the number of columns in a result set. |
| mysql_num_rows() | Returns the number of rows in a result set. |
| mysql_options() | Sets connect options for mysql_connect(). |
| mysql_ping() | Checks whether the connection to the server is working, reconnecting as necessary. |
| mysql_query() | Executes an SQL query specified as a null-terminated string. |
| mysql_real_connect() | Connects to a MySQL server. |
| mysql_real_escape_string() | Escapes special characters in a string for use in an SQL statement, taking into account the current character set of the connection. |
| mysql_real_query() | Executes an SQL query specified as a counted string. |
| mysql_refresh() | Flush or reset tables and caches. |
| mysql_reload() | Tells the server to reload the grant tables. |
| mysql_rollback() | Rolls back the transaction. |
| mysql_row_seek() | Seeks to a row offset in a result set, using value returned from
mysql_row_tell(). |
| mysql_row_tell() | Returns the row cursor position. |
| mysql_select_db() | Selects a database. |
| mysql_server_end() | Finalize embedded server library. |
| mysql_server_init() | Initialize embedded server library. |
| mysql_set_local_infile_default() | Set the LOAD DATA LOCAL INFILE handler callbacks to
their default values. |
| mysql_set_local_infile_handler() | Install application-specific LOAD DATA LOCAL INFILE
handler callbacks. |
| mysql_set_server_option() | Sets an option for the connection (like
multi-statements). |
| mysql_sqlstate() | Returns the SQLSTATE error code for the last error. |
| mysql_shutdown() | Shuts down the database server. |
| mysql_stat() | Returns the server status as a string. |
| mysql_store_result() | Retrieves a complete result set to the client. |
| mysql_thread_id() | Returns the current thread ID. |
| mysql_thread_safe() | Returns 1 if the clients are compiled as thread-safe. |
| mysql_use_result() | Initiates a row-by-row result set retrieval. |
| mysql_warning_count() | Returns the warning count for the previous SQL statement. |
Application programs should use this general outline for interacting with MySQL:
Initialize the MySQL library by calling
mysql_library_init(). The library can be
either the mysqlclient C client library
or the mysqld embedded server library,
depending on whether the application was linked with the
-libmysqlclient or
-libmysqld flag.
Initialize a connection handler by calling
mysql_init() and connect to the server by
calling mysql_real_connect().
Issue SQL statements and process their results. (The following discussion provides more information about how to do this.)
Close the connection to the MySQL server by calling
mysql_close().
End use of the MySQL library by calling
mysql_library_end().
The purpose of calling mysql_library_init()
and mysql_library_end() is to provide proper
initialization and finalization of the MySQL library. For
applications that are linked with the client library, they
provide improved memory management. If you don't call
mysql_library_end(), a block of memory
remains allocated. (This does not increase the amount of memory
used by the application, but some memory leak detectors will
complain about it.) For applications that are linked with the
embedded server, these calls start and stop the server.
mysql_library_init() and
mysql_library_end() are available as of MySQL
5.0.3. These actually are #define symbols
that make them equivalent to
mysql_server_init() and
mysql_server_end(), but the names more
clearly indicate that they should be called when beginning and
ending use of a MySQL library no matter whether the application
uses the mysqlclient or
mysqld library. For older versions of MySQL,
you can call mysql_server_init() and
mysql_server_end() instead.
In a non-multi-threaded environment, the call to
mysql_library_init() may be omitted, because
mysql_init() will invoke it automatically as
necessary. However, a race condition is possible if
mysql_library_init() is invoked by
mysql_init() in a multi-threaded environment:
mysql_library_init() is not thread-safe, so
it should be called prior to any other client library call.
To connect to the server, call mysql_init()
to initialize a connection handler, then call
mysql_real_connect() with that handler (along
with other information such as the hostname, username, and
password). Upon connection,
mysql_real_connect() sets the
reconnect flag (part of the
MYSQL structure) to a value of
1 in versions of the API older than 5.0.3, or
0 in newer versions. A value of
1 for this flag indicates that if a statement
cannot be performed because of a lost connection, to try
reconnecting to the server before giving up. As of MySQL 5.0.13,
you can use the MYSQL_OPT_RECONNECT option to
mysql_options() to control reconnection
behavior. When you are done with the connection, call
mysql_close() to terminate it.
While a connection is active, the client may send SQL statements
to the server using mysql_query() or
mysql_real_query(). The difference between
the two is that mysql_query() expects the
query to be specified as a null-terminated string whereas
mysql_real_query() expects a counted string.
If the string contains binary data (which may include null
bytes), you must use mysql_real_query().
For each non-SELECT query (for example,
INSERT, UPDATE,
DELETE), you can find out how many rows were
changed (affected) by calling
mysql_affected_rows().
For SELECT queries, you retrieve the selected
rows as a result set. (Note that some statements are
SELECT-like in that they return rows. These
include SHOW, DESCRIBE,
and EXPLAIN. They should be treated the same
way as SELECT statements.)
There are two ways for a client to process result sets. One way
is to retrieve the entire result set all at once by calling
mysql_store_result(). This function acquires
from the server all the rows returned by the query and stores
them in the client. The second way is for the client to initiate
a row-by-row result set retrieval by calling
mysql_use_result(). This function initializes
the retrieval, but does not actually get any rows from the
server.
In both cases, you access rows by calling
mysql_fetch_row(). With
mysql_store_result(),
mysql_fetch_row() accesses rows that have
previously been fetched from the server. With
mysql_use_result(),
mysql_fetch_row() actually retrieves the row
from the server. Information about the size of the data in each
row is available by calling
mysql_fetch_lengths().
After you are done with a result set, call
mysql_free_result() to free the memory used
for it.
The two retrieval mechanisms are complementary. Client programs
should choose the approach that is most appropriate for their
requirements. In practice, clients tend to use
mysql_store_result() more commonly.
An advantage of mysql_store_result() is that
because the rows have all been fetched to the client, you not
only can access rows sequentially, you can move back and forth
in the result set using mysql_data_seek() or
mysql_row_seek() to change the current row
position within the result set. You can also find out how many
rows there are by calling mysql_num_rows().
On the other hand, the memory requirements for
mysql_store_result() may be very high for
large result sets and you are more likely to encounter
out-of-memory conditions.
An advantage of mysql_use_result() is that
the client requires less memory for the result set because it
maintains only one row at a time (and because there is less
allocation overhead, mysql_use_result() can
be faster). Disadvantages are that you must process each row
quickly to avoid tying up the server, you don't have random
access to rows within the result set (you can only access rows
sequentially), and you don't know how many rows are in the
result set until you have retrieved them all. Furthermore, you
must retrieve all the rows even
if you determine in mid-retrieval that you've found the
information you were looking for.
The API makes it possible for clients to respond appropriately
to statements (retrieving rows only as necessary) without
knowing whether the statement is a SELECT.
You can do this by calling
mysql_store_result() after each
mysql_query() (or
mysql_real_query()). If the result set call
succeeds, the statement was a SELECT and you
can read the rows. If the result set call fails, call
mysql_field_count() to determine whether a
result was actually to be expected. If
mysql_field_count() returns zero, the
statement returned no data (indicating that it was an
INSERT, UPDATE,
DELETE, and so forth), and was not expected
to return rows. If mysql_field_count() is
non-zero, the statement should have returned rows, but didn't.
This indicates that the statement was a
SELECT that failed. See the description for
mysql_field_count() for an example of how
this can be done.
Both mysql_store_result() and
mysql_use_result() allow you to obtain
information about the fields that make up the result set (the
number of fields, their names and types, and so forth). You can
access field information sequentially within the row by calling
mysql_fetch_field() repeatedly, or by field
number within the row by calling
mysql_fetch_field_direct(). The current field
cursor position may be changed by calling
mysql_field_seek(). Setting the field cursor
affects subsequent calls to
mysql_fetch_field(). You can also get
information for fields all at once by calling
mysql_fetch_fields().
For detecting and reporting errors, MySQL provides access to
error information by means of the
mysql_errno() and
mysql_error() functions. These return the
error code or error message for the most recently invoked
function that can succeed or fail, allowing you to determine
when an error occurred and what it was.
In the descriptions here, a parameter or return value of
NULL means NULL in the
sense of the C programming language, not a MySQL
NULL value.
Functions that return a value generally return a pointer or an
integer. Unless specified otherwise, functions returning a
pointer return a non-NULL value to indicate
success or a NULL value to indicate an error,
and functions returning an integer return zero to indicate
success or non-zero to indicate an error. Note that
“non-zero” means just that. Unless the function
description says otherwise, do not test against a value other
than zero:
if (result) /* correct */
... error ...
if (result < 0) /* incorrect */
... error ...
if (result == -1) /* incorrect */
... error ...
When a function returns an error, the
Errors subsection of the
function description lists the possible types of errors. You can
find out which of these occurred by calling
mysql_errno(). A string representation of the
error may be obtained by calling
mysql_error().
my_ulonglong mysql_affected_rows(MYSQL
*mysql)
Description
Returns the number of rows changed by the last
UPDATE, deleted by the last
DELETE or inserted by the last
INSERT statement. May be called immediately
after mysql_query() for
UPDATE, DELETE, or
INSERT statements. For
SELECT statements,
mysql_affected_rows() works like
mysql_num_rows().
Return Values
An integer greater than zero indicates the number of rows
affected or retrieved. Zero indicates that no records were
updated for an UPDATE statement, no rows
matched the WHERE clause in the query or
that no query has yet been executed. -1 indicates that the
query returned an error or that, for a
SELECT query,
mysql_affected_rows() was called prior to
calling mysql_store_result(). Because
mysql_affected_rows() returns an unsigned
value, you can check for -1 by comparing the return value to
(my_ulonglong)-1 (or to
(my_ulonglong)~0, which is equivalent).
Errors
None.
Example
mysql_query(&mysql,"UPDATE products SET cost=cost*1.25 WHERE group=10");
printf("%ld products updated",(long) mysql_affected_rows(&mysql));
If you specify the flag CLIENT_FOUND_ROWS
when connecting to mysqld,
mysql_affected_rows() returns the number of
rows matched by the WHERE statement for
UPDATE statements. Otherwise, it returns
the number of rows actually changed.
Note that when you use a REPLACE command,
mysql_affected_rows() returns 2 if the new
row replaced an old row, because in this case, one row was
inserted after the duplicate was deleted.
If you use INSERT ... ON DUPLICATE KEY
UPDATE to insert a row,
mysql_affected_rows() returns 1 if the row
is inserted as a new row and 2 if an existing row is updated.
my_bool mysql_autocommit(MYSQL *mysql, my_bool
mode)
Description
Sets autocommit mode on if mode is 1, off
if mode is 0.
Return Values
Zero if successful. Non-zero if an error occurred.
Errors
None.
my_bool mysql_change_user(MYSQL *mysql, const char
*user, const char *password, const char *db)
Description
Changes the user and causes the database specified by
db to become the default (current) database
on the connection specified by mysql. In
subsequent queries, this database is the default for table
references that do not include an explicit database specifier.
mysql_change_user() fails if the connected
user cannot be authenticated or doesn't have permission to use
the database. In this case, the user and database are not
changed
The db parameter may be set to
NULL if you don't want to have a default
database.
This command always performs a ROLLBACK of
any active transactions, closes all temporary tables, unlocks
all locked tables and resets the state as if one had done a
new connect. This happens even if the user didn't change.
Return Values
Zero for success. Non-zero if an error occurred.
Errors
The same that you can get from
mysql_real_connect().
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
ER_UNKNOWN_COM_ERROR
The MySQL server doesn't implement this command (probably an old server).
ER_ACCESS_DENIED_ERROR
The user or password was wrong.
ER_BAD_DB_ERROR
The database didn't exist.
ER_DBACCESS_DENIED_ERROR
The user did not have access rights to the database.
ER_WRONG_DB_NAME
The database name was too long.
Example
if (mysql_change_user(&mysql, "user", "password", "new_database"))
{
fprintf(stderr, "Failed to change user. Error: %s\n",
mysql_error(&mysql));
}
const char *mysql_character_set_name(MYSQL
*mysql)
Description
Returns the default character set for the current connection.
Return Values
The default character set
Errors
None.
void mysql_close(MYSQL *mysql)
Description
Closes a previously opened connection.
mysql_close() also deallocates the
connection handle pointed to by mysql if
the handle was allocated automatically by
mysql_init() or
mysql_connect().
Return Values
None.
Errors
None.
my_bool mysql_commit(MYSQL *mysql)
Description
Commits the current transaction.
As of MySQL 5.0.3, the action of this function is subject to
the value of the completion_type system
variable. In particular, if the value of
completion_type is 2, the server performs a
release after terminating a transaction and closes the client
connection. The client program should call
mysql_close() to close the connection from
the client side.
Return Values
Zero if successful. Non-zero if an error occurred.
Errors
None.
MYSQL *mysql_connect(MYSQL *mysql, const char *host,
const char *user, const char *passwd)
Description
This function is deprecated. It is preferable to use
mysql_real_connect() instead.
mysql_connect() attempts to establish a
connection to a MySQL database engine running on
host. mysql_connect()
must complete successfully before you can execute any of the
other API functions, with the exception of
mysql_get_client_info().
The meanings of the parameters are the same as for the
corresponding parameters for
mysql_real_connect() with the difference
that the connection parameter may be NULL.
In this case, the C API allocates memory for the connection
structure automatically and frees it when you call
mysql_close(). The disadvantage of this
approach is that you can't retrieve an error message if the
connection fails. (To get error information from
mysql_errno() or
mysql_error(), you must provide a valid
MYSQL pointer.)
Return Values
Same as for mysql_real_connect().
Errors
Same as for mysql_real_connect().
int mysql_create_db(MYSQL *mysql, const char
*db)
Description
Creates the database named by the db
parameter.
This function is deprecated. It is preferable to use
mysql_query() to issue an SQL
CREATE DATABASE statement instead.
Return Values
Zero if the database was created successfully. Non-zero if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
Example
if(mysql_create_db(&mysql, "my_database"))
{
fprintf(stderr, "Failed to create new database. Error: %s\n",
mysql_error(&mysql));
}
void mysql_data_seek(MYSQL_RES *result, my_ulonglong
offset)
Description
Seeks to an arbitrary row in a query result set. The
offset value is a row number and should be
in the range from 0 to
mysql_num_rows(result)-1.
This function requires that the result set structure contains
the entire result of the query, so
mysql_data_seek() may be used only in
conjunction with mysql_store_result(), not
with mysql_use_result().
Return Values
None.
Errors
None.
void mysql_debug(const char *debug)
Description
Does a DBUG_PUSH with the given string.
mysql_debug() uses the Fred Fish debug
library. To use this function, you must compile the client
library to support debugging. See
Section E.1, “Debugging a MySQL Server”, and
Section E.2, “Debugging a MySQL Client”.
Return Values
None.
Errors
None.
Example
The call shown here causes the client library to generate a
trace file in /tmp/client.trace on the
client machine:
mysql_debug("d:t:O,/tmp/client.trace");
int mysql_drop_db(MYSQL *mysql, const char
*db)
Description
Drops the database named by the db
parameter.
This function is deprecated. It is preferable to use
mysql_query() to issue an SQL DROP
DATABASE statement instead.
Return Values
Zero if the database was dropped successfully. Non-zero if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
Example
if(mysql_drop_db(&mysql, "my_database"))
fprintf(stderr, "Failed to drop the database: Error: %s\n",
mysql_error(&mysql));
int mysql_dump_debug_info(MYSQL *mysql)
Description
Instructs the server to write some debug information to the
log. For this to work, the connected user must have the
SUPER privilege.
Return Values
Zero if the command was successful. Non-zero if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
my_bool mysql_eof(MYSQL_RES *result)
Description
This function is deprecated. mysql_errno()
or mysql_error() may be used instead.
mysql_eof() determines whether the last row
of a result set has been read.
If you acquire a result set from a successful call to
mysql_store_result(), the client receives
the entire set in one operation. In this case, a
NULL return from
mysql_fetch_row() always means the end of
the result set has been reached and it is unnecessary to call
mysql_eof(). When used with
mysql_store_result(),
mysql_eof() always returns true.
On the other hand, if you use
mysql_use_result() to initiate a result set
retrieval, the rows of the set are obtained from the server
one by one as you call mysql_fetch_row()
repeatedly. Because an error may occur on the connection
during this process, a NULL return value
from mysql_fetch_row() does not necessarily
mean the end of the result set was reached normally. In this
case, you can use mysql_eof() to determine
what happened. mysql_eof() returns a
non-zero value if the end of the result set was reached and
zero if an error occurred.
Historically, mysql_eof() predates the
standard MySQL error functions
mysql_errno() and
mysql_error(). Because those error
functions provide the same information, their use is preferred
over mysql_eof(), which is deprecated. (In
fact, they provide more information, because
mysql_eof() returns only a boolean value
whereas the error functions indicate a reason for the error
when one occurs.)
Return Values
Zero if no error occurred. Non-zero if the end of the result set has been reached.
Errors
None.
Example
The following example shows how you might use
mysql_eof():
mysql_query(&mysql,"SELECT * FROM some_table");
result = mysql_use_result(&mysql);
while((row = mysql_fetch_row(result)))
{
// do something with data
}
if(!mysql_eof(result)) // mysql_fetch_row() failed due to an error
{
fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
}
However, you can achieve the same effect with the standard MySQL error functions:
mysql_query(&mysql,"SELECT * FROM some_table");
result = mysql_use_result(&mysql);
while((row = mysql_fetch_row(result)))
{
// do something with data
}
if(mysql_errno(&mysql)) // mysql_fetch_row() failed due to an error
{
fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
}
unsigned int mysql_errno(MYSQL *mysql)
Description
For the connection specified by mysql,
mysql_errno() returns the error code for
the most recently invoked API function that can succeed or
fail. A return value of zero means that no error occurred.
Client error message numbers are listed in the MySQL
errmsg.h header file. Server error
message numbers are listed in
mysqld_error.h. Errors also are listed at
Appendix B, Error Codes and Messages.
Note that some functions like
mysql_fetch_row() don't set
mysql_errno() if they succeed.
A rule of thumb is that all functions that have to ask the
server for information reset mysql_errno()
if they succeed.
Return Values
An error code value for the last
mysql_
call, if it failed. zero means no error occurred.
xxx()
Errors
None.
const char *mysql_error(MYSQL *mysql)
Description
For the connection specified by mysql,
mysql_error() returns a null-terminated
string containing the error message for the most recently
invoked API function that failed. If a function didn't fail,
the return value of mysql_error() may be
the previous error or an empty string to indicate no error.
A rule of thumb is that all functions that have to ask the
server for information reset mysql_error()
if they succeed.
For functions that reset mysql_errno(), the
following two tests are equivalent:
if(mysql_errno(&mysql))
{
// an error occurred
}
if(mysql_error(&mysql)[0] != '\0')
{
// an error occurred
}
The language of the client error messages may be changed by recompiling the MySQL client library. Currently, you can choose error messages in several different languages. See Section 5.11.2, “Setting the Error Message Language”.
Return Values
A null-terminated character string that describes the error. An empty string if no error occurred.
Errors
None.
You should use mysql_real_escape_string()
instead!
This function is identical to
mysql_real_escape_string() except that
mysql_real_escape_string() takes a
connection handler as its first argument and escapes the
string according to the current character set.
mysql_escape_string() does not take a
connection argument and does not respect the current character
set.
MYSQL_FIELD *mysql_fetch_field(MYSQL_RES
*result)
Description
Returns the definition of one column of a result set as a
MYSQL_FIELD structure. Call this function
repeatedly to retrieve information about all columns in the
result set. mysql_fetch_field() returns
NULL when no more fields are left.
mysql_fetch_field() is reset to return
information about the first field each time you execute a new
SELECT query. The field returned by
mysql_fetch_field() is also affected by
calls to mysql_field_seek().
If you've called mysql_query() to perform a
SELECT on a table but have not called
mysql_store_result(), MySQL returns the
default blob length (8KB) if you call
mysql_fetch_field() to ask for the length
of a BLOB field. (The 8KB size is chosen
because MySQL doesn't know the maximum length for the
BLOB. This should be made configurable
sometime.) Once you've retrieved the result set,
field->max_length contains the length of
the largest value for this column in the specific query.
Return Values
The MYSQL_FIELD structure for the current
column. NULL if no columns are left.
Errors
None.
Example
MYSQL_FIELD *field;
while((field = mysql_fetch_field(result)))
{
printf("field name %s\n", field->name);
}
MYSQL_FIELD *mysql_fetch_field_direct(MYSQL_RES
*result, unsigned int fieldnr)
Description
Given a field number fieldnr for a column
within a result set, returns that column's field definition as
a MYSQL_FIELD structure. You may use this
function to retrieve the definition for an arbitrary column.
The value of fieldnr should be in the range
from 0 to mysql_num_fields(result)-1.
Return Values
The MYSQL_FIELD structure for the specified
column.
Errors
None.
Example
unsigned int num_fields;
unsigned int i;
MYSQL_FIELD *field;
num_fields = mysql_num_fields(result);
for(i = 0; i < num_fields; i++)
{
field = mysql_fetch_field_direct(result, i);
printf("Field %u is %s\n", i, field->name);
}
MYSQL_FIELD *mysql_fetch_fields(MYSQL_RES
*result)
Description
Returns an array of all MYSQL_FIELD
structures for a result set. Each structure provides the field
definition for one column of the result set.
Return Values
An array of MYSQL_FIELD structures for all
columns of a result set.
Errors
None.
Example
unsigned int num_fields;
unsigned int i;
MYSQL_FIELD *fields;
num_fields = mysql_num_fields(result);
fields = mysql_fetch_fields(result);
for(i = 0; i < num_fields; i++)
{
printf("Field %u is %s\n", i, fields[i].name);
}
unsigned long *mysql_fetch_lengths(MYSQL_RES
*result)
Description
Returns the lengths of the columns of the current row within a
result set. If you plan to copy field values, this length
information is also useful for optimization, because you can
avoid calling strlen(). In addition, if the
result set contains binary data, you
must use this function to
determine the size of the data, because
strlen() returns incorrect results for any
field containing null characters.
The length for empty columns and for columns containing
NULL values is zero. To see how to
distinguish these two cases, see the description for
mysql_fetch_row().
Return Values
An array of unsigned long integers representing the size of
each column (not including any terminating null characters).
NULL if an error occurred.
Errors
mysql_fetch_lengths() is valid only for the
current row of the result set. It returns
NULL if you call it before calling
mysql_fetch_row() or after retrieving all
rows in the result.
Example
MYSQL_ROW row;
unsigned long *lengths;
unsigned int num_fields;
unsigned int i;
row = mysql_fetch_row(result);
if (row)
{
num_fields = mysql_num_fields(result);
lengths = mysql_fetch_lengths(result);
for(i = 0; i < num_fields; i++)
{
printf("Column %u is %lu bytes in length.\n", i, lengths[i]);
}
}
MYSQL_ROW mysql_fetch_row(MYSQL_RES
*result)
Description
Retrieves the next row of a result set. When used after
mysql_store_result(),
mysql_fetch_row() returns
NULL when there are no more rows to
retrieve. When used after
mysql_use_result(),
mysql_fetch_row() returns
NULL when there are no more rows to
retrieve or if an error occurred.
The number of values in the row is given by
mysql_num_fields(result). If
row holds the return value from a call to
mysql_fetch_row(), pointers to the values
are accessed as row[0] to
row[mysql_num_fields(result)-1].
NULL values in the row are indicated by
NULL pointers.
The lengths of the field values in the row may be obtained by
calling mysql_fetch_lengths(). Empty fields
and fields containing NULL both have length
0; you can distinguish these by checking the pointer for the
field value. If the pointer is NULL, the
field is NULL; otherwise, the field is
empty.
Return Values
A MYSQL_ROW structure for the next row.
NULL if there are no more rows to retrieve
or if an error occurred.
Errors
Note that error is not reset between calls to
mysql_fetch_row()
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
Example
MYSQL_ROW row;
unsigned int num_fields;
unsigned int i;
num_fields = mysql_num_fields(result);
while ((row = mysql_fetch_row(result)))
{
unsigned long *lengths;
lengths = mysql_fetch_lengths(result);
for(i = 0; i < num_fields; i++)
{
printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL");
}
printf("\n");
}
unsigned int mysql_field_count(MYSQL
*mysql)
Description
Returns the number of columns for the most recent query on the connection.
The normal use of this function is when
mysql_store_result() returned
NULL (and thus you have no result set
pointer). In this case, you can call
mysql_field_count() to determine whether
mysql_store_result() should have produced a
non-empty result. This allows the client program to take
proper action without knowing whether the query was a
SELECT (or SELECT-like)
statement. The example shown here illustrates how this may be
done.
Return Values
An unsigned integer representing the number of columns in a result set.
Errors
None.
Example
MYSQL_RES *result;
unsigned int num_fields;
unsigned int num_rows;
if (mysql_query(&mysql,query_string))
{
// error
}
else // query succeeded, process any data returned by it
{
result = mysql_store_result(&mysql);
if (result) // there are rows
{
num_fields = mysql_num_fields(result);
// retrieve rows, then call mysql_free_result(result)
}
else // mysql_store_result() returned nothing; should it have?
{
if(mysql_field_count(&mysql) == 0)
{
// query does not return data
// (it was not a SELECT)
num_rows = mysql_affected_rows(&mysql);
}
else // mysql_store_result() should have returned data
{
fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
}
}
}
An alternative is to replace the
mysql_field_count(&mysql) call with
mysql_errno(&mysql). In this case, you
are checking directly for an error from
mysql_store_result() rather than inferring
from the value of mysql_field_count()
whether the statement was a SELECT.
MYSQL_FIELD_OFFSET mysql_field_seek(MYSQL_RES
*result, MYSQL_FIELD_OFFSET offset)
Description
Sets the field cursor to the given offset. The next call to
mysql_fetch_field() retrieves the field
definition of the column associated with that offset.
To seek to the beginning of a row, pass an
offset value of zero.
Return Values
The previous value of the field cursor.
Errors
None.
MYSQL_FIELD_OFFSET mysql_field_tell(MYSQL_RES
*result)
Description
Returns the position of the field cursor used for the last
mysql_fetch_field(). This value can be used
as an argument to mysql_field_seek().
Return Values
The current offset of the field cursor.
Errors
None.
void mysql_free_result(MYSQL_RES *result)
Description
Frees the memory allocated for a result set by
mysql_store_result(),
mysql_use_result(),
mysql_list_dbs(), and so forth. When you
are done with a result set, you must free the memory it uses
by calling mysql_free_result().
Do not attempt to access a result set after freeing it.
Return Values
None.
Errors
None.
void mysql_get_character_set_info(MYSQL *mysql,
MY_CHARSET_INFO *cs)
Description
This function provides information about the default client
character set. The default character set may be changed with
the mysql_set_character_set() function.
This function was added in MySQL 5.0.10.
Example
if (!mysql_set_character_set(&mysql, "utf8"))
{
MY_CHARSET_INFO cs;
mysql_get_character_set_info(&mysql, &cs);
printf("character set information:\n");
printf("character set name: %s\n", cs.name);
printf("collation name: %s\n", cs.csname);
printf("comment: %s\n", cs.comment);
printf("directory: %s\n", cs.dir);
printf("multi byte character min. length: %d\n", cs.mbminlen);
printf("multi byte character max. length: %d\n", cs.mbmaxlen);
}
char *mysql_get_client_info(void)
Description
Returns a string that represents the client library version.
Return Values
A character string that represents the MySQL client library version.
Errors
None.
unsigned long
mysql_get_client_version(void)
Description
Returns an integer that represents the client library version.
The value has the format XYYZZ where
X is the major version,
YY is the release level, and
ZZ is the version number within the release
level. For example, a value of 40102
represents a client library version of
4.1.2.
Return Values
An integer that represents the MySQL client library version.
Errors
None.
char *mysql_get_host_info(MYSQL *mysql)
Description
Returns a string describing the type of connection in use, including the server hostname.
Return Values
A character string representing the server hostname and the connection type.
Errors
None.
unsigned int mysql_get_proto_info(MYSQL
*mysql)
Description
Returns the protocol version used by current connection.
Return Values
An unsigned integer representing the protocol version used by the current connection.
Errors
None.
char *mysql_get_server_info(MYSQL *mysql)
Description
Returns a string that represents the server version number.
Return Values
A character string that represents the server version number.
Errors
None.
unsigned long mysql_get_server_version(MYSQL
*mysql)
Description
Returns the version number of the server as an integer.
Return Values
A number that represents the MySQL server version in this format:
major_version*10000 + minor_version *100 + sub_version
For example, 5.0.12 is returned as 50012.
This function is useful in client programs for quickly determining whether some version-specific server capability exists.
Errors
None.
unsigned long mysql_hex_string(char *to, const char
*from, unsigned long length)
Description
This function is used to create a legal SQL string that you can use in an SQL statement. See Section 9.1.1, “Strings”.
The string in from is encoded to
hexadecimal format, with each character encoded as two
hexadecimal digits. The result is placed in
to and a terminating null byte is appended.
The string pointed to by from must be
length bytes long. You must allocate the
to buffer to be at least
length*2+1 bytes long. When
mysql_hex_string() returns, the contents of
to is a null-terminated string. The return
value is the length of the encoded string, not including the
terminating null character.
The return value can be placed into an SQL statement using
either 0x
or valueX'
format. However, the return value does not include the
value'0x or X'...'. The caller
must supply whichever of those is desired.
Example
char query[1000],*end;
end = strmov(query,"INSERT INTO test_table values(");
end = strmov(end,"0x");
end += mysql_hex_string(end,"What's this",11);
end = strmov(end,",0x");
end += mysql_hex_string(end,"binary data: \0\r\n",16);
*end++ = ')';
if (mysql_real_query(&mysql,query,(unsigned int) (end - query)))
{
fprintf(stderr, "Failed to insert row, Error: %s\n",
mysql_error(&mysql));
}
The strmov() function used in the example
is included in the mysqlclient library and
works like strcpy() but returns a pointer
to the terminating null of the first parameter.
Return Values
The length of the value placed into to, not
including the terminating null character.
Errors
None.
char *mysql_info(MYSQL *mysql)
Description
Retrieves a string providing information about the most
recently executed query, but only for the statements listed
here. For other statements, mysql_info()
returns NULL. The format of the string
varies depending on the type of query, as described here. The
numbers are illustrative only; the string contains values
appropriate for the query.
INSERT INTO ... SELECT ...
String format: Records: 100 Duplicates: 0
Warnings: 0
INSERT INTO ... VALUES
(...),(...),(...)...
String format: Records: 3 Duplicates: 0 Warnings:
0
LOAD DATA INFILE ...
String format: Records: 1 Deleted: 0 Skipped: 0
Warnings: 0
ALTER TABLE
String format: Records: 3 Duplicates: 0 Warnings:
0
UPDATE
String format: Rows matched: 40 Changed: 40
Warnings: 0
Note that mysql_info() returns a
non-NULL value for INSERT ...
VALUES only for the multiple-row form of the
statement (that is, only if multiple value lists are
specified).
Return Values
A character string representing additional information about
the most recently executed query. NULL if
no information is available for the query.
Errors
None.
MYSQL *mysql_init(MYSQL *mysql)
Description
Allocates or initializes a MYSQL object
suitable for mysql_real_connect(). If
mysql is a NULL pointer,
the function allocates, initializes, and returns a new object.
Otherwise, the object is initialized and the address of the
object is returned. If mysql_init()
allocates a new object, it is freed when
mysql_close() is called to close the
connection.
Return Values
An initialized MYSQL* handle.
NULL if there was insufficient memory to
allocate a new object.
Errors
In case of insufficient memory, NULL is
returned.
my_ulonglong mysql_insert_id(MYSQL *mysql)
Description
Returns the value generated for an
AUTO_INCREMENT column by the previous
INSERT or UPDATE
statement. Use this function after you have performed an
INSERT statement into a table that contains
an AUTO_INCREMENT field.
More precisely, mysql_insert_id() is
updated under these conditions:
INSERT statements that store a value
into an AUTO_INCREMENT column. This is
true whether the value is automatically generated by
storing the special values NULL or
0 into the column, or is an explicit
non-special value.
In the case of a multiple-row INSERT
statement, mysql_insert_id() returns
the first automatically
generated AUTO_INCREMENT value; if no
such value is generated, it returns the last
last explicit value
inserted into the AUTO_INCREMENT
column.
INSERT statements that generate an
AUTO_INCREMENT value by inserting
LAST_INSERT_ID(
into any column.
expr)
INSERT statements that generate an
AUTO_INCREMENT value by updating any
column to
LAST_INSERT_ID(.
expr)
The value of mysql_insert_id() is not
affected by statements such as SELECT
that return a result set.
If the previous statement returned an error, the value of
mysql_insert_id() is undefined.
Note that mysql_insert_id() returns
0 if the previous statement does not use an
AUTO_INCREMENT value. If you need to save
the value for later, be sure to call
mysql_insert_id() immediately after the
statement that generates the value.
The value of mysql_insert_id() is affected
only by statements issued within the current client
connection. It is not affected by statements issued by other
clients.
See Section 12.9.3, “Information Functions”.
Also note that the value of the SQL
LAST_INSERT_ID() function always contains
the most recently generated AUTO_INCREMENT
value, and is not reset between statements because the value
of that function is maintained in the server. Another
difference is that LAST_INSERT_ID() is not
updated if you set an AUTO_INCREMENT column
to a specific non-special value.
The reason for the difference between
LAST_INSERT_ID() and
mysql_insert_id() is that
LAST_INSERT_ID() is made easy to use in
scripts while mysql_insert_id() tries to
provide a little more exact information of what happens to the
AUTO_INCREMENT column.
Return Values
Described in the preceding discussion.
Errors
None.
int mysql_kill(MYSQL *mysql, unsigned long
pid)
Description
Asks the server to kill the thread specified by
pid.
Return Values
Zero for success. Non-zero if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
void mysql_library_end(void)
Description
This is a synonym for the
mysql_server_end() function. It was added
in MySQL 5.0.3.
See Section 22.2.2, “C API Function Overview”, for usage information.
int mysql_library_init(int argc, char **argv, char
**groups)
Description
This is a synonym for the
mysql_server_init() function. It was added
in MySQL 5.0.3. See Section 22.2.12.1, “mysql_server_init()”.
See Section 22.2.2, “C API Function Overview” for usage information.
MYSQL_RES *mysql_list_dbs(MYSQL *mysql, const char
*wild)
Description
Returns a result set consisting of database names on the
server that match the simple regular expression specified by
the wild parameter. wild
may contain the wildcard characters
‘%’ or
‘_’, or may be a
NULL pointer to match all databases.
Calling mysql_list_dbs() is similar to
executing the query SHOW databases [LIKE
wild].
You must free the result set with
mysql_free_result().
Return Values
A MYSQL_RES result set for success.
NULL if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_OUT_OF_MEMORY
Out of memory.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
MYSQL_RES *mysql_list_fields(MYSQL *mysql, const char
*table, const char *wild)
Description
Returns a result set consisting of field names in the given
table that match the simple regular expression specified by
the wild parameter. wild
may contain the wildcard characters
‘%’ or
‘_’, or may be a
NULL pointer to match all fields. Calling
mysql_list_fields() is similar to executing
the query SHOW COLUMNS FROM
.
tbl_name [LIKE
wild]
Note that it's recommended that you use SHOW COLUMNS
FROM instead of
tbl_namemysql_list_fields().
You must free the result set with
mysql_free_result().
Return Values
A MYSQL_RES result set for success.
NULL if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
MYSQL_RES *mysql_list_processes(MYSQL
*mysql)
Description
Returns a result set describing the current server threads.
This is the same kind of information as that reported by
mysqladmin processlist or a SHOW
PROCESSLIST query.
You must free the result set with
mysql_free_result().
Return Values
A MYSQL_RES result set for success.
NULL if an error occurred.
Errors
CR_COMMANDS_OUT_OF_SYNC
Commands were executed in an improper order.
CR_SERVER_GONE_ERROR
The MySQL server has gone away.
CR_SERVER_LOST
The connection to the server was lost during the query.
CR_UNKNOWN_ERROR
An unknown error occurred.
MYSQL_RES *mysql_list_tables(MYSQL *mysql, const char
*wild)
Description
Returns a result set consisting of table names in the current
database that match the simple regular expression specified by
the wild parameter. wild
may contain the wildcard characters
‘%’ or
‘_’, or may be a
NULL pointer to match all tables. Calling