1.待求证
2.alter table Sbasic add constraint PK_Sbasic primary key(sno)
3.alter table SC add constraint PK_SC primary key(sno,cno)
4.alter table SC add constraint PK_SC foreign key(sno) references Sbasic(sno)
5.create unique index ID_SC on SC(sno)
2.alter table Sbasic add constraint PK_Sbasic primary key(sno)
3.alter table SC add constraint PK_SC primary key(sno,cno)
4.alter table SC add constraint PK_SC foreign key(sno) references Sbasic(sno)
5.create unique index ID_SC on SC(sno)
1: alter table sbasic add constraint df_grade default(0) with grade
2: alter table sbasic add constraint pk_sbasic primary key (sno)
3: alter table sc add constraint pk_sc primary key (sno,cno)
4: alter table sc add constraint fk_sc refrence sbacic(sno)
5: create unique index id_sc on sc (sno)
alter table Sbasic add constraint PK_Sbasic primary key(sno)
alter table SC add constraint PK_SC primary key(cno)
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那上面有
alter table SC drop column grade
alter table SC add grade int constraint DF_grade default(0)