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索引的删除 有两种方法
第一: drop index index_name on tb_name; 第二: alter table tb_name drop index index_name;
创建一个表,添加索引
mysql> create table tb4 ( age int , name varchar(20), email varchar(20)); Query OK, 0 rows affected (0.26 sec) mysql> alter table tb4 add index (age); Query OK, 0 rows affected (0.50 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> alter table tb4 add unique (name); Query OK, 0 rows affected (0.47 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> create index index_name on tb4 (email); Query OK, 0 rows affected (0.65 sec) Records: 0 Duplicates: 0 Warnings: 0
查看当前的索引
mysql> show index from tb4; +-------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | tb4 | 0 | name | 1 | name | A | 0 | NULL | NULL | YES | BTREE | | | | tb4 | 1 | age | 1 | age | A | 0 | NULL | NULL | YES | BTREE | | | | tb4 | 1 | index_name | 1 | email | A | 0 | NULL | NULL | YES | BTREE | | | +-------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ 3 rows in set (0.00 sec)
删除索引
mysql> alter table tb4 drop index name; Query OK, 0 rows affected (0.12 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> alter table tb4 drop index index_name; Query OK, 0 rows affected (0.11 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> drop index age on tb4; Query OK, 0 rows affected (0.13 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> mysql> show index from tb4; Empty set (0.00 sec)
索引的删除,都是删除的索引的名字, 如果创建索引的时候,没有指定名字, 那么名字就只字段的名字。
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