MySQL的計數顯示更多的結果比預期

Question

這裏是我的查詢：

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON active.AGENTUID = mls.MSTLISTBRD 
    AND mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing'; 

的表是相當大的，所以這將是難以顯示錶結構。

當我運行沒有AND mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing'的計數，我得到一個預期的結果（約500）。但是當我想用這些參數過濾掉時，它會返回25000+個結果，當它應該在500以下時。

我想這是一個語法問題，但查找類似的問題，我無法想出一個解決方案。

Answer 1

使用WHERE條款

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON active.AGENTUID = mls.MSTLISTBRD 
    WHERE mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing'; 

Answer 2

SELECT COUNT(*) 
    FROM jos_mls mls 
    JOIN jos_activeagents active 
    ON active.AGENTUID = mls.MSTLISTBRD 
    AND (mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing'); 

或

SELECT COUNT(*) 
    FROM jos_mls mls 
    JOIN jos_activeagents active 
    ON active.AGENTUID = mls.MSTLISTBRD 
    AND mls.MSTACTSTA IN('Active','Keep Showing'); 

Answer 3

AND的優先級高於OR所以你應該使用周圍的狀況的第二部分括號來獲得所需的輸出：

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON active.AGENTUID = mls.MSTLISTBRD 
    AND (mls.MSTACTSTA = 'Active' OR mls.MSTACTSTA = 'Keep Showing'); 

你得到比預計多了很多行的原因是運行實際的查詢是相同的，因爲這一個：建議

SELECT COUNT(*) FROM jos_mls AS mls 
    INNER JOIN jos_activeagents AS active ON (active.AGENTUID = mls.MSTLISTBRD 
    AND mls.MSTACTSTA = 'Active') OR mls.MSTACTSTA = 'Keep Showing';