インデックスを表示 [From|IN]
ステートメントSHOW INDEXES [FROM|IN]は、指定されたテーブルのインデックスを一覧表示します。ステートメントSHOW INDEX [FROM|IN] 、 SHOW KEYS [FROM|IN]はこのステートメントのエイリアスであり、MySQL との互換性のために含まれています。
あらすじ
ShowIndexStmt:
ShowIndexKwd:
FromOrIn:
テーブル名:
ShowLikeOrWhereOpt:
例
mysql> CREATE TABLE t1 (id int not null primary key AUTO_INCREMENT, col1 INT, INDEX(col1));
Query OK, 0 rows affected (0.12 sec)
mysql> SHOW INDEXES FROM t1;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| t1 | 0 | PRIMARY | 1 | id | A | 0 | NULL | NULL | | BTREE | | | YES
| NULL |
| t1 | 1 | col1 | 1 | col1 | A | 0 | NULL | NULL | YES | BTREE | | | YES
| NULL |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
2 rows in set (0.00 sec)
mysql> SHOW INDEX FROM t1;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| t1 | 0 | PRIMARY | 1 | id | A | 0 | NULL | NULL | | BTREE | | | YES
| NULL |
| t1 | 1 | col1 | 1 | col1 | A | 0 | NULL | NULL | YES | BTREE | | | YES
| NULL |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
2 rows in set (0.00 sec)
mysql> SHOW KEYS FROM t1;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Visible | Expression |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
| t1 | 0 | PRIMARY | 1 | id | A | 0 | NULL | NULL | | BTREE | | | YES
| NULL |
| t1 | 1 | col1 | 1 | col1 | A | 0 | NULL | NULL | YES | BTREE | | | YES
| NULL |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+---------+------------+
2 rows in set (0.00 sec)
MySQL の互換性
MySQL のCardinality列は、インデックスの異なる値の数を示します。 TiDB では、 Cardinality列には常に0が表示されます。