假设供应商S和供应情况SPJ的关系模式分别为：S(Sno，Sname，Status，City)和SPJ(Sno，Pno，Jno，Qty)。SQL语句(22)不能正确地查询出“零件号Pno等于‘P3’的供应商名Sname”，而(23)能正确查询的关系代数表达式。A.SELECT DISTINCT Sname FROMS WHERE EXISTS(SELECT* FROM SPJ WHERE S. Sno=SPJ. SnO AND SPJ.Pno='P3')B.SELECT DISTmCT Sname FROMS WHERE 0＜(SEIECT COUNT(*)FROM SPJ WHERES.Sno=SPJ.Sno AND SPJ.Pno='P3')C.SELECT Sname FROMS WHERE EXISTS(SELECT* FROM SPJ WHERES.Sno=SPJ.Sno ANDSPJ.Pno='P3')D.SELECT Sname FROMS，SPJ WHERES.Sno=SPJ.Sno ANDSPJ.Pno='P3')GROUP BYSname
A.SELECT
B.Pno='P3')
B.SELECT
C.Sno=SPJ.Sno
D.Pno='P3')
C.SELECT
E.Sno=SPJ.Sno
F.Pno='P3')
D.SELECT
G.Sno=SPJ.Sno
H.Pno='P3')GROUP