SELECT b.employeeid,(COUNT(DISTINCT a.customerid) FROM orders a,employees b WHERE b.是否工作 = 'y' AND b.employeeid = a.employeeid(+) GROUP BY b.employeeid
SELECT B.employeeid, COUNT((DISTINCT B.customerid)) FROM (SELECT employeeid FROM employees WHERE employees.是否工作 = 'Y') A, orders B WHERE A.employeeid = B.employeeid GROUP BY B.employeeid; 雁南兄,我这样也没错吧。 性能方面,跟你的比有差别吗?
FROM orders a,employees b
WHERE b.是否工作 = 'y'
AND b.employeeid = a.employeeid(+)
GROUP BY b.employeeid
(SELECT employeeid FROM employees WHERE employees.是否工作 = 'Y') A, orders B
WHERE A.employeeid = B.employeeid
GROUP BY B.employeeid;
雁南兄,我这样也没错吧。
性能方面,跟你的比有差别吗?