----------------MODIFY--------------------------------------------------
某列定义非空约束
SQL>ALTER TABLE office_organization
>MODIFY(desc VARCHAR2(20)
>CONSTRAINT nn_desc NOT NULL)
某列定义唯一关键字
SQL>ALTER TABLE office_organization
>MODIFY(office_name VATCHAR2(20)
>CONSTRAINT uq_officename UNIQUE)
----------------ADD--------------------------------------------------
ALTER TABLE jxzy.switch
>ADD (DESC VARCHAR2(30));
----------------DISABLE---------------------------------------------
使主键约束无效
SQL>ALTER TABLE switch DISABLE PRIMARY KEY