设销售数据模型如下:厂家S(SNO,SNAME,CITY)产品P(PNO,PNAME,COLOR,WEIGHT)工程J(JNO,JNAME,CITY)
设销售数据模型如下:
厂家S(SNO,SNAME,CITY)
产品P(PNO,PNAME,COLOR,WEIGHT)
工程J(JNO,JNAME,CITY)
销售SPJ(SNO,PNO,JNO,QTY)
用SQL完成查询:与“双青”在同一城市的厂家名.
SELECT S.SNAME
FROM S,S AS X
WHERE X.SNAME=’双青’
AND S.CITY=X.CITY;