SELECT DISTINCT SPJ.JNO,JNAME,SPJ.PNO,PNAME,SUM(QTY)
FROM SPJ,P,J
WHERE JNAME IN (SELECT JNAME
FROM J
WHERE J.JNO=SPJ.JNO)
AND
PNAME IN (SELECT PNAME
FROM P
WHERE P.PNO=SPJ.PNO)
GROUP BY SPJ.JNO,JNAME,SPJ.PNO,PNAME
ORDER BY SPJ.JNO ASC,SUM(QTY)DESC;

写法明显有笛卡儿积，哪怕你用 DISTINCT 也是徒劳的
改成：
SELECT SPJ.JNO,JNAME,SPJ.PNO,PNAME,SUM(QTY)
FROM SPJ,P,J
WHERE
J.JNO=SPJ.JNO
AND P.PNO=SPJ.PNO
GROUP BY SPJ.JNO,JNAME,SPJ.PNO,PNAME
ORDER BY SPJ.JNO ASC,SUM(QTY)DESC;