title: SHOW INDEXES [FROM|IN] summary: TiDB 数据库中 SHOW INDEXES [FROM|IN] 的使用概况。

SHOW INDEXES [FROM|IN]

SHOW INDEXES [FROM|IN] 语句用于列出指定表上的索引。SHOW INDEX [FROM | IN] 和 SHOW KEYS [FROM | IN] 是该语句的别名。包含该语句提供了 MySQL 兼容性。

语法图

ShowIndexStmt:

ShowIndexStmt

ShowIndexKwd:

ShowIndexKwd

FromOrIn:

FromOrIn

TableName:

TableName

ShowLikeOrWhereOpt:

ShowLikeOrWhereOpt

示例

  1. CREATE TABLE t1 (id int not null primary key AUTO_INCREMENT, col1 INT, INDEX(col1));
  1. Query OK, 0 rows affected (0.12 sec)
  1. SHOW INDEXES FROM t1;
  1. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  2. | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
  3. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  4. | t1    |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               | YES 
  5.     | NULL       |
  6. | t1    |          1 | col1     |            1 | col1        | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               | YES 
  7.     | NULL       |
  8. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  9. 2 rows in set (0.00 sec)
  1. SHOW INDEX FROM t1;
  1. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  2. | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
  3. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  4. | t1    |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               | YES 
  5.     | NULL       |
  6. | t1    |          1 | col1     |            1 | col1        | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               | YES 
  7.     | NULL       |
  8. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  9. 2 rows in set (0.00 sec)
  1. SHOW KEYS FROM t1;
  1. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  2. | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
  3. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  4. | t1    |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               | YES 
  5.     | NULL       |
  6. | t1    |          1 | col1     |            1 | col1        | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               | YES 
  7.     | NULL       |
  8. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
  9. 2 rows in set (0.00 sec)

MySQL 兼容性

MySQL 中的 Cardinality 列返回该索引上不同值的个数，而 TiDB 中的 Cardinality 列始终返回 0。

另请参阅