约束定义所在的数据字典: all_constraints dba_constraints user_constraints
all_con_columns dba_con_columns user_con_columns
select distinct constraint_type form user_constraints R:references针对列 U:unique针对列 P:primary key针对列 C:check针对列 O:read only针对视图 v:Check option on a view:针对视图
平时查询: select * from dba_constraints where table_name='CDE01';
当物化视图或级联更新时,要用到索引的延迟属性,即不马上验证,等到提交时再验证。 not deferrable与deferrable区别: 区别就在于: “立即验证的可延迟约束” 是可以根据需要设置成 “延迟验证的可延迟约束”的, 而“不可延迟验证”是不能改变的. 比如: alter table cde01 add constraint cde01_name_chk check(length(name)>2) deferrable initially deferred; 可以修改: set constraint CDE01_name_chk immediate; set constraint CDE01_name_chk deferred; 默认创建的约束是 not deferrable |