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リストします。ステートメントSHOW INDEX [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SHOW KEYS [FROM|IN]ます。
あらすじ
ShowIndexStmt：
ShowIndexKwd：
FromOrIn：
TableName：
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、インデックスのさまざまな値の数を示しています。 TiDBでは、 Cardinality列には常に0が表示されます。