SHOW INDEXES [FROM|IN]

    ShowIndexStmt:

    ShowIndexKwd:

    FromOrIn:

    FromOrIn

    TableName:

    ShowLikeOrWhereOpt:

    1. Query OK, 0 rows affected (0.12 sec)
    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 
    8. 2 rows in set (0.00 sec)
    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. | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
    2. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
    3. | t1    |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               | YES 
    4.     | NULL       |
    5. | t1    |          1 | col1     |            1 | col1        | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               | YES 
    6.     | NULL       |
    7. +-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
    8. 2 rows in set (0.00 sec)

    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 。