WITH ROLLUP的不正確使用和DISTINCT

Question

我嘗試導入SQL文件MySQL數據庫，但我遇到一個問題：

ERROR 1221 (HY000) at line 4598: Incorrect usage of WITH ROLLUP and DISTINCT 

DROP PROCEDURE IF EXISTS `sp_employees_rollup`$$ 
CREATE PROCEDURE `sp_employees_rollup`() 
BEGIN 
SELECT Distinct City ,Sum(Salary) Salary_By_City FROM employees 
GROUP BY City WITH ROLLUP; 

END $$ 

DELIMITER ; 

Answer 1

你並不需要在GROUP BY查詢中使用DISTINCT City，因爲，因爲每個記錄結果集將已經不同。改爲使用此查詢：

SELECT City 
     SUM(Salary) Salary_By_City 
FROM employees 
GROUP BY City WITH ROLLUP