数据库查询语句大全,数据库SQL查询语句 5分

数据库查询语句大全,数据库SQL查询语句 5分

(我不太清楚你说的课程号是指CNO还是CNAME,我这里假定你说的课程号为CNO，以下语句均未考虑字段数值类型)
1、SELECt A1.SNO,A1.SNAME,A2.GRADE FROM S A1,SC A2 WHERe A1.SNO = A2.SNO AND A2.CNO = C2 AND A2.GRADE BETWEEN 80 AND 90
2、不太懂
3、SELECt A1.SNO FROM SC A1,SC A2 WHERe A1.SNO = A2.SNO AND A1.CNO = C2 AND
A2.CNO = C4 GROUP BY A1.SNO
4、SELECt A1.SNO FROM SC A1 WHERe A1.CNO = C1 AND A1.SNO NOT IN (SELECt SNO FROM SC WHERe CNO = C2)
5、SELECt A1.SNO,A1.SNAME,A1.AGE FROM S A1,SC A2 WHERe A1.SNO = A2.SNO AND A2.CNO NOT IN(C1,C2)
6、SELECt SNO,SNAME FROM S WHERe SNO NOT IN(
SELECt SNO FROM SC WHERe GRADE

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