MySQL用子查詢評估案例

我正在嘗試創建一個自定義排序，該排序涉及另一個表中某些記錄的計數。例如，如果一個記錄在另一個表中沒有與其關聯的記錄，則它應該在排序中看起來高於具有一個或多個記錄的記錄。這是我到目前爲止：MySQL用子查詢評估案例

SELECT People.*, Organizations.Name AS Organization_Name, 
    (CASE 
     WHEN Sent IS NULL AND COUNT(SELECT * FROM Graphics WHERE People.Organization_ID = Graphics.Organization_ID) = 0 THEN 0 
     ELSE 1 
    END) AS Status 
FROM People 
LEFT JOIN Organizations ON Organizations.ID = People.Organization_ID 
ORDER BY Status ASC

COUNT內的子查詢不起作用。什麼是這樣做的正確方法？

更新：我感動case語句到order by條款，並增加了join：

SELECT People.*, Organizations.Name AS Organization_Name 
FROM People 
LEFT JOIN Organizations ON Organizations.ID = People.Organization_ID 
LEFT JOIN Graphics ON Graphics.Organization_ID = People.Organization_ID 
GROUP BY People.ID 
ORDER BY 
    CASE 
    WHEN Sent IS NULL AND Graphics.ID IS NULL THEN 0 
    ELSE 1 
    END ASC

所以，如果如果People記錄沒有任何圖形，Graphics.ID將是無效的。這實現了迫切需要。

來源

2012-02-27 Andrew

這裏有什麼問題？ – AndreKR 2012-02-27 18:44:05

如果你試圖不通過加入對一個子查詢，置CASE表達成ORDER BY以及工作，這是可以做到：

SELECT 
    People.*, 
    orgcount.num 
FROM People JOIN (
    SELECT Organization_ID, COUNT(*) AS num FROM Graphics GROUP BY Organization_ID 
) orgcount ON People.Organization_ID = orgcount.num 
ORDER BY 
    CASE WHEN Sent IS NULL AND orgcount.num = 0 THEN 0 ELSE 1 END, 
    orgcount.num DESC

來源

2012-02-27 18:48:08

你可以使用一個外部連接的圖形表獲取你的排序所需的數據。

因爲我不知道你的模式，所以我假定People表有一個名爲ID的主鍵列。如果PK欄的名稱不同，則應替換GROUP BY子句中的名稱。與JOIN只要你有某種在人民表，以集團的主鍵的左

SELECT People.*, (count(Distinct Graphics.Organization_ID) > 0) as Status 
FROM People 
LEFT OUTER JOIN Graphics ON People.Organization_ID = Graphics.Organization_ID 
GROUP BY People.ID 
ORDER BY Status ASC

來源

2012-02-27 18:53:26

相當直截了當;：

像這樣的東西應該爲你工作

SELECT p.*, sent IS NOT NULL or COUNT(g.Organization_ID) Status 
FROM People p LEFT JOIN Graphics g ON g.Organization_ID = p.Organization_ID 
GROUP BY p.primary_key 
ORDER BY Status

演示here。

來源

2012-02-27 19:08:45

MySQL用子查詢評估案例

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