Oracle 數據完整性的維護

1.刪除約束  
alter table table_name drop constraint constraint_name;  
2.創建主鍵  
alter table table_name add constraint constraint_name primary key(column_name1,column_name2);   -
 

3.創建唯一約束  
alter table table_name add constraint constraint_name unique(column_name1,column_name2);  
4.創建外鍵約束  
alter table table_name1 add constraint constraint_name foreign key(column_name1) references table_name2(column_name1);  
enable/disable：約束/不約束新數據  
novalidate/validate:不對/對老數據進行驗證  
alter table table_name add constraint constraint_name check(column_name like 'B%') enable/disable novalidate/validate;  
5.修改約束條件，延時驗證，commit時驗證  
alter table table_name modify constraint constraint_name initially deferred;  
6.修改約束條件，立即驗證  
alter table table_name modify constraint constraint_name initially immediate;  
7.設置約束延遲/立即驗證  
alter session set constraints=deferred/immediate;  
8.刪除表時刪除約束  
drop一個有外鍵的主鍵表,帶cascade constraints參數級聯刪除  
drop table table_name cascade constraints;  
9.當truncate外鍵表時，先將外鍵設為無效，再truncate;  
truncate table table_name;  
設約束條件無效  
alter table table_name disable constraint constraint_name;  
alter table table_name enable novalidate constraint constraint_name
 

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