PostgreSQL 添加各种约束语法

PostgreSQL 添加各种约束语法

1. 添加主键

alter table goods add primary key(sid);

2. 添加外键

alter table orders add foreign key(goods_id) references goods(sid) on update cascade on delete cascade;

on update cascade: 被引用行更新时,引用行自动更新;

on update restrict: 被引用的行禁止更新;

on delete cascade: 被引用行删除时,引用行也一起删除;

on dellete restrict: 被引用的行禁止删除;

3. 删除外键

alter table orders drop constraint orders_goods_id_fkey;

4. 添加唯一约束

alter table goods add constraint unique_goods_sid unique(sid);

5. 删除默认值

alter table goods alter column sid drop default;

6. 修改字段的数据类型

alter table goods alter column sid type character varying;

7. 重命名字段

alter table goods rename column sid to ssid;

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