查询存在” 01 “课程但可能不存在” 02 “课程的情况select * from(select SC.SId, SC.score from SC where SC.CId = ’01’) as t1 left join(select SC.SId, SC.score from SC where SC.CId = ’02’) as t2 on t1.SId = t2.SId()
判断题
查询存在” 01 “课程但可能不存在” 02 “课程的情况select * from(select SC.SId, SC.score from SC where SC.CId = ’01’) as t1 left join(select SC.SId, SC.score from SC where SC.CId = ’02’) as t2 on t1.SId = t2.SId()