Sql Server约束

主键约束

alter table TblTeacher add constraint PK_TblTeacher_tTId primary key(tTId)

外键约束

         alter table TblScore add constraint FK_TblScore_tSid foreign key(tSid) references TblStudent(tSid) on delete cascade on update cascade

on delete cascade on update cascade 这句话是级联更新删除操作

唯一约束

         alter table TblScore add constraint UQ_TblScore_tEnglish unique(tEnglish)

默认约束

         alter table TblScore add constraint DF_TblScore_TMath default(10) for TMath

检查约束

         alter table TblScore add constraint CK_TblScore_TMath check(TMath>=10 and TMath<=100)

非空约束

         alter table TblScore alter column tMath int not null