在实现 INFORMATION_SCHEMA 时，SHOW 语句的一些扩展被引入：Some extensions to SHOW statements accompany the implementation of INFORMATION_SCHEMA:

INFORMATION_SCHEMA 是一个信息数据库，因此它的名称会包含在 SHOW DATABASES 的输出中。类似地，SHOW TABLES 可以与 INFORMATION_SCHEMA 一起使用，以获取其表的列表：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                     |
| ENGINES                               |
| EVENTS                                |
| FILES                                 |
| KEY_COLUMN_USAGE                      |
| PARTITIONS                            |
| PLUGINS                               |
| PROCESSLIST                           |
| REFERENTIAL_CONSTRAINTS               |
| ROUTINES                              |
| SCHEMATA                              |
| SCHEMA_PRIVILEGES                     |
| STATISTICS                            |
| TABLES                                |
| TABLE_CONSTRAINTS                     |
| TABLE_PRIVILEGES                      |
| TRIGGERS                              |
| USER_PRIVILEGES                       |
| VIEWS                                 |
+---------------------------------------+

SHOW COLUMNS 和 DESCRIBE 可以显示单个 INFORMATION_SCHEMA 表中列的信息。SHOW COLUMNS and DESCRIBE can display information about the columns in individual INFORMATION_SCHEMA tables.

SHOW 语句接受 LIKE 子句来限制显示的行，同时也允许使用 WHERE 子句来指定选中行必须满足的一般条件：SHOW statements that accept a LIKE clause to limit the rows displayed also permit a WHERE clause that specifies more general conditions that selected rows must satisfy:

SHOW CHARACTER SET
SHOW COLLATION
SHOW COLUMNS
SHOW DATABASES
SHOW FUNCTION STATUS
SHOW INDEX
SHOW OPEN TABLES
SHOW PROCEDURE STATUS
SHOW STATUS
SHOW TABLE STATUS
SHOW TABLES
SHOW TRIGGERS
SHOW VARIABLES

如果存在，WHERE 子句会根据 SHOW 语句显示的列名进行评估。例如，SHOW CHARACTER SET 语句生成以下输出列：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 |
...

要在 SHOW CHARACTER SET 中使用 WHERE 子句，你需要引用这些列名。例如，以下语句显示默认排序规则包含字符串 'japanese' 的字符集信息：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 |
+---------+---------------------------+---------------------+--------+

该语句显示多字节字符集：This statement displays the multibyte character sets:

mysql> SHOW CHARACTER SET WHERE Maxlen > 1;
+---------+---------------------------------+---------------------+--------+
| Charset | Description                     | Default collation   | Maxlen |
+---------+---------------------------------+---------------------+--------+
| big5    | Big5 Traditional Chinese        | big5_chinese_ci     |      2 |
| cp932   | SJIS for Windows Japanese       | cp932_japanese_ci   |      2 |
| eucjpms | UJIS for Windows Japanese       | eucjpms_japanese_ci |      3 |
| euckr   | EUC-KR Korean                   | euckr_korean_ci     |      2 |
| gb18030 | China National Standard GB18030 | gb18030_chinese_ci  |      4 |
| gb2312  | GB2312 Simplified Chinese       | gb2312_chinese_ci   |      2 |
| gbk     | GBK Simplified Chinese          | gbk_chinese_ci      |      2 |
| sjis    | Shift-JIS Japanese              | sjis_japanese_ci    |      2 |
| ucs2    | UCS-2 Unicode                   | ucs2_general_ci     |      2 |
| ujis    | EUC-JP Japanese                 | ujis_japanese_ci    |      3 |
| utf16   | UTF-16 Unicode                  | utf16_general_ci    |      4 |
| utf16le | UTF-16LE Unicode                | utf16le_general_ci  |      4 |
| utf32   | UTF-32 Unicode                  | utf32_general_ci    |      4 |
| utf8mb3 | UTF-8 Unicode                   | utf8mb3_general_ci  |      3 |
| utf8mb4 | UTF-8 Unicode                   | utf8mb4_0900_ai_ci  |      4 |
+---------+---------------------------------+---------------------+--------+