drop table if exists SC; create table SC( Sno char(10), Cno char(10), Grade smallint not null, constraint pk_sno primary key (sno,cno) ) 首先简单创建一个表,并为其插入主码 Insert Into SC (Sno ,Cno,Grade) Values ('2000011111','1000000001',88), ('2000011111','1000000004',88) 并向其中插入一些数据,这里简单示范