1、创建/删除索引：
mysql> create index idx_wtest_id on wtest(id);---创建
Query OK, 0 rows affected (1.19 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> drop index idx_wtest_id on wtest;----删除
Query OK, 0 rows affected (0.42 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table t3 add unique uni_t3_idx(id);--创建唯一索引
Query OK, 0 rows affected (0.42 sec)
Records: 0 Duplicates: 0 Warnings: 0
2、添加删除主键：
mysql> alter table wtest add primary key pk_wtest(id);---创建
Query OK, 1 row affected (1.35 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> alter table wtest drop primary key ;----删除
Query OK, 1 row affected (1.41 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> alter table t3 modify id int auto_increment;------修改为主键自增
Query OK, 4 rows affected (0.70 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql>
mysql> create index idx_wtest_id on wtest(id);---创建
Query OK, 0 rows affected (1.19 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> drop index idx_wtest_id on wtest;----删除
Query OK, 0 rows affected (0.42 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table t3 add unique uni_t3_idx(id);--创建唯一索引
Query OK, 0 rows affected (0.42 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> alter table wtest add primary key pk_wtest(id);---创建
Query OK, 1 row affected (1.35 sec)
Records: 1 Duplicates: 0 Warnings: 0
Query OK, 1 row affected (1.41 sec)
Records: 1 Duplicates: 0 Warnings: 0
mysql> alter table t3 modify id int auto_increment;------修改为主键自增
Query OK, 4 rows affected (0.70 sec)
Records: 4 Duplicates: 0 Warnings: 0
mysql>
3、查看索引信息：
mysql> show index from custcontactinfo;
+-----------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-----------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| custcontactinfo | 0 | PRIMARY | 1 | id | A | 185468 | NULL | NULL | | BTREE | | |
| custcontactinfo | 1 | idx_custcontactinfo_idcard | 1 | IDCARD | A | 185468 | NULL | NULL | YES | BTREE | | |
+-----------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
mysql> show index from custcontactinfo;
+-----------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-----------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| custcontactinfo | 0 | PRIMARY | 1 | id | A | 185468 | NULL | NULL | | BTREE | | |
| custcontactinfo | 1 | idx_custcontactinfo_idcard | 1 | IDCARD | A | 185468 | NULL | NULL | YES | BTREE | | |
+-----------------+------------+----------------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/10569970/viewspace-1744505/ ，如需转载，请注明出处，否则将追究法律责任。
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