现在有两个关系模式：供应商S(Sno，Sname，Status，City)和供应情况
题型：单项选择题
问题：
现在有两个关系模式：供应商S(Sno，Sname，Status，City)和供应情况SPJ(Sno，Pno，Jno， Qty)。对于查询“查询零件号Pno等于‘P3’的供应商名Sname”SQL语句 (221) 是错误的，而关系代数表达式 (222) 是正确的。
A．SELECTSname FROM S WHERE EXIST5 (SELECT * FROM SPJ WHERE S.Sno＝SPJ.Sno AND SPJ.Pno＝’P3’)
B．SELECT Sname FROM S,SPJ WHERE S.Sno＝SPJ.Sno AND SPJ.Pno＝’P3’) CROUP BY Sname
C．SELECT DISTINCT Sname FROM S WHERE EXISTS (SELECT * FROM SPJ WHERE S.Sno＝SPJ.Sno AND SPJ.Pno＝’P3’)
D．SELECT DISTINCT Sname FROM S WHERERE 0＜ (SELECTCOUNT(，) FROM SPJ WHERE S.Sno＝SPJ.Sno AND SPJ.Pnn＝’P3’)