oracle 序列，check约束

====================序列

//查询当前用户序列

select * from user_sequences

//查询所有序列

select * from all_sequences;

//创建序列

语法：create sequence 表名_sequence increment by 1 start with 1 nomaxvalue nocycle;

eg:

create sequence third_party_merchant_sequence increment by 1 start with 1 nomaxvalue nocycle;

//查询该序列的下一个值

select THIRD_PARTY_MERCHANT_SEQUENCE.Nextval from dual;

删除序列：

drop sequence third_party_merchant_sequence;

========================check约束

启用约束: enable( validate) :启用约束,创建索引,对已有及新加入的数据执行约束. enable novalidate :启用约束,创建索引,仅对新加入的数据强制执行约束,而不管表中的现有数据.

禁用约束: disable( novalidate):关闭约束,删除索引,可以对约束列的数据进行修改等操作. disable validate :关闭约束,删除索引,不能对表进行插入/更新/删除等操作.

//查询当前用户约束

select * from user_constraints;

//创建表时添加约束

create table test

(id int,

name varchar2(10),

sex varchar2(10) check (sex in ('男','女'))

);

//为表添加约束

alter table THIRD_PARTY_MERCHANT
add constraint constraint_yn
check(yn in(1,2))enable validate;

//删除约束
alter table THIRD_PARTY_MERCHANT drop constraint constraint_yn;commit;

//重新添加

alter table THIRD_PARTY_MERCHANT
add constraint constraint_yn
check(yn in(1,0))enable validate;

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