PostgreSQL alter语法

增加列：

alter table products add column description text;

alter table products add column description text check (description <> '');

删除列：

alter table products drop column description

alter table products drop column description cascade;

增加约束：

alter table products add check (name <> '');

alter table products add constraint some_name unique (product_no);

alter table products add foreign key (product_group_id) references product_groups;

移除约束:

alter table products drop constraint some_name;

alter table products alter column product_no drop not null;

修改默认值：

alter table products alter column price set default 7.77;

alter table products alter column price drop default;

修改数据类型：

alter table products alter column price type numeric(10,2);

列重命名：

alter table products rename column product_no to product_number;

表重命名：

alter table products rename to items;

修改所有者：

alter table table_name owner to new_owner;