唯一索引

2024年06月12日

柏拉文

越努力，越幸运

一、认识

---

唯一索引确保索引中的值是唯一的，不允许有重复值。

二、创建索引

---

2.1 create unique index [indexName] on [tableName] ([columnName1][asc|desc], [columnName2][asc|desc], ……)

create unique index [indexName] on [tableName] ([columnName1][asc|desc], [columnName2][asc|desc], ……);

2.2 alter table [tableName] add constraint [uniqueConstraintName] unique ([columnName1][asc|desc], [columnName2][asc|desc], ……);

alter table [tableName] add constraint [uniqueConstraintName] unique ([columnName1][asc|desc], [columnName2][asc|desc], ……);

2.3 create table [tableName] (……, constraint [indexName] unique ([columnName1][asc|desc], [columnName2][asc|desc], ……) )

create table [tableName] (
    column1 dateType,
    column2 dateType,
    constraint [indexName] unique ([columnName1][asc|desc], [columnName2][asc|desc], ……)
)

三、删除索引

---

3.1 drop index [indexName] on [tableName]

drop index [indexName] on [tableName];

3.2 alter table [tableName] drop index [indexName]

alter table [tableName] drop index [indexName];

四、查看索引

---

4.1 show index from [tableName]\G

show index from [tableName]\G;