| 索引类型 | 建表时 | 建表后 |
|---|---|---|
| 主键索引 | create table t(id int primary key); create table t(id int, primary key(id)); |
alter table t add primary key(id); |
| 单值索引 | create table t(a int, index(a)); create table t(a int, key(a)); create table t(a int, index index_name (a)); |
alter table t add index (a); alter table t add key (a); alter table t add index index_name (a); alter table t add key key_name (a); create index index_name on t(a); |
| 唯一索引 | create table t(a int unique); create table t(a int, unique(a)); create table t(a int, unique unique_name (a)); create table t(a int, unique index index_name (a)); create table t(a int, unique key key_name (a)); |
alter table t add unique (a); alter table t add unique unique_name (a); alter table t add unique index (a); alter table t add unique key (a); alter table t add unique index index_name (a); alter table t add unique key key_name (a); create unique index index_name on t(a); |
| 复合索引 | create table t(a int, b int, index(a,b)); create table t(a int, b int, key(a,b)); create table t(a int, b int, index index _name (a,b)); create table t(a int, b int, key key_name (a,b)); |
alter table t add index (a,b); alter table t add key (a,b); alter table t add index index_name (a,b); alter table t add key key_name (a,b); create index index_name on t(a,b); |
Mysql-索引创建,索引失效案例
2024-03-27 14:00:04 69 阅读
