oracle 数据完整性的维护

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　　1.删除约束alter table table_name drop constraint constraint_name;2.创建主键alter table table_name add constraint constraint_name primary key(column_name1,column_name2);3.创建唯一约束alter table table_name add constraint constraint_name unique(column_name1,column_name2);4.创建外键约束alter table table_name1 add constraint constraint_name foreign key(column_name1) references table_name2(column_name1);enable/disable：约束/不约束新数据novalidate/validate:不对/对老数据进行验证alter table table_name add constraint constraint_name check(column_name like 'B%') enable/disable novalidate/validate;5.修改约束条件，延时验证，commit时验证alter table table_name modify constraint constraint_name initially deferred;6.修改约束条件，立即验证alter table table_name modify constraint constraint_name initially immediate;7.设置约束延迟/立即验证alter session set constraints=deferred/immediate;8.删除表时删除约束drop一个有外键的主键表,带cascade constraints参数级联删除drop table table_name cascade constraints;9.当truncate外键表时，先将外键设为无效，再truncate;truncate table table_name;设约束条件无效alter table table_name disable constraint constraint_name;alter table table_name enable novalidate constraint constraint_name;