Some extensions to SHOW statements accompany
the implementation of INFORMATION_SCHEMA:
SHOW can be used to get information about
the structure of INFORMATION_SCHEMA itself.
Several SHOW statements accept a
WHERE clause that provides more flexibility
in specifying which rows to display.
These extensions are available beginning with MySQL 5.0.3.
INFORMATION_SCHEMA is an information database,
so its name is included in the output from SHOW
DATABASES. Similarly, SHOW TABLES can
be used with INFORMATION_SCHEMA to obtain a
list of its tables:
mysql> SHOW TABLES FROM INFORMATION_SCHEMA;
+---------------------------------------+
| Tables_in_information_schema |
+---------------------------------------+
| CHARACTER_SETS |
| COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS |
| COLUMN_PRIVILEGES |
| KEY_COLUMN_USAGE |
| ROUTINES |
| SCHEMATA |
| SCHEMA_PRIVILEGES |
| STATISTICS |
| TABLES |
| TABLE_CONSTRAINTS |
| TABLE_PRIVILEGES |
| TRIGGERS |
| USER_PRIVILEGES |
| VIEWS |
+---------------------------------------+
16 rows in set (0.00 sec)
SHOW COLUMNS and DESCRIBE
can display information about the columns in individual
INFORMATION_SCHEMA tables.
Several SHOW statement have been extended to
allow a WHERE clause:
SHOW CHARACTER SET SHOW COLLATION SHOW COLUMNS SHOW DATABASES SHOW FUNCTION STATUS SHOW KEYS SHOW OPEN TABLES SHOW PROCEDURE STATUS SHOW STATUS SHOW TABLE STATUS SHOW TABLES SHOW VARIABLES
The WHERE clause, if present, is evaluated
against the column names displayed by the SHOW
statement. For example, the SHOW CHARACTER SET
statement produces these output columns:
mysql> SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
...
To use a WHERE clause with SHOW
CHARACTER SET, you would refer to those column names. As
an example, the following statement displays information about
character sets for which the default collation contains the string
'japanese':
mysql> SHOW CHARACTER SET WHERE `Default collation` LIKE '%japanese%';
+---------+---------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+---------+---------------------------+---------------------+--------+
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
+---------+---------------------------+---------------------+--------+
This statement displays the multi-byte character sets:
mysql> SHOW CHARACTER SET WHERE Maxlen > 1;
+---------+---------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+---------+---------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
+---------+---------------------------+---------------------+--------+