如何根據兩行條件選擇列值？

Question

Name  Username Day worked Time period 
---------------------------------------------- 
John Doe john  Sunday  8 
Tom  tom   Monday  10 
Jane Doe jane  Tuesday  5 
John Doe john  Friday  9 

查詢：

SELECT username FROM table WHERE (day_worked='Sunday' AND time_period>5) AND (day_worked='Friday' and time_period>8) 

這裏我申請條件的兩列，用戶誰在週日超過5小時和週五超過8小時的工作。顯然，John Doe（用戶名：john）符合條件，應該輸出。

但是這不會返回任何東西。可能是我使用的邏輯是錯誤的。有任何想法嗎？

Answer 1

你可以通過一些交叉製表魔法來做到這一點。首先，交叉製表所有用戶在週日和週五：

SELECT 
    username, 
    SUM(CASE WHEN `Day worked` = 'Sunday' THEN `Time Period` END) As Sunday, 
    SUM(CASE WHEN `Day worked` = 'Friday' THEN `Time Period` END) AS Friday 
FROM table 
GROUP BY username 

這個查詢將產生以下

username Sunday Friday 
-------- ------ ------ 
jane  NULL NULL 
john  8  9 
tom  NULL NULL 

通過推動這個結果分解成一個子查詢，你可以很容易地挑選出誰工作5個多小時，星期日及8小時以上週五：

SELECT username 
FROM (
    SELECT 
    username, 
     SUM(CASE WHEN `Day worked` = 'Sunday' THEN `Time Period` END) As Sunday, 
     SUM(CASE WHEN `Day worked` = 'Friday' THEN `Time Period` END) AS Friday 
    FROM table 
    GROUP BY username 
) SunFri 
WHERE SunFri.Sunday > 5 AND SunFri.Friday > 8 

Answer 2

您可以檢查此查詢是給你想要的結果

SELECT username FROM table 
INNER JOIN table T2 ON table.Username = T2.Username AND (day_worked='Friday' and time_period>8) 
WHERE (day_worked='Sunday' AND time_period>5) 

其更好地張貼sqlfiddle我們一起工作。

Answer 3

SELECT username 
    FROM table 
WHERE (day_worked='Sunday' AND time_period>5)   
    OR (day_worked='Friday' and time_period>8) 
GROUP 
    BY username 
HAVING COUNT(*) = 2