为什么这给出一个空的结果?我试图获得不是监督员的一组员工的最小值,最大值和平均值。职员表的SQL聚合不产生结果
SELECT MIN(salary), MAX(salary), AVG(salary)
FROM employee
WHERE ssn NOT IN
(SELECT superssn FROM employee)
部分
SSN SUPERSSN
--------- ---------
888665555
333445555 888665555
987654321 888665555
987987987 987654321
123456789 333445555
999887777 987654321
666884444 333445555
453453453 333445555
什么'select count(ssn)FROM employee WHERE ssn NOT IN(SELECT superssn FROM employee)'给你 – 2011-05-12 04:50:35