MySQL和查詢中使用兩次不起作用

Question

下面的查詢

SELECT * FROM workshops 
WHERE workshop_zipcode LIKE '75___' 
    OR workshop_zipcode LIKE '77___' 
    AND workshop_category = 14 
    AND active = 1 
    AND workshop_date >= NOW() 
ORDER BY workshop_date ASC 

不會產生任何錯誤，和實際工作，但有一個小問題：這一部分

AND workshop_date >= NOW() 

不要過濾任何東西，以相同的方式替換比較符號，並檢索相同的列表。

兩個第一個AND效果不錯，但第三個不行。

Answer 1

你需要圓括號您OR條件像這樣：

SELECT * FROM workshops 
WHERE (workshop_zipcode LIKE '75___' 
OR workshop_zipcode LIKE '77___') 
AND workshop_category = 14 
AND active = 1 
AND workshop_date >= NOW() 
ORDER BY workshop_date ASC 

如果沒有括號，你在本質上調用此：

SELECT * FROM workshops 
WHERE workshop_zipcode LIKE '75___' 
OR (workshop_zipcode LIKE '77___' 
AND workshop_category = 14 
AND active = 1 
AND workshop_date >= NOW()) 
ORDER BY workshop_date ASC 

這是因爲AND是在之前計算的。看到這個參考

http://dev.mysql.com/doc/refman/5.0/en/operator-precedence.html

Answer 2

嘗試這樣的：

SELECT * FROM workshops 
WHERE (workshop_zipcode LIKE '75___' 
OR workshop_zipcode LIKE '77___') 
AND workshop_category = 14 
AND active = 1 
AND workshop_date >= NOW() 
ORDER BY workshop_date ASC 

Answer 3

這可能是與運算符優先級的問題。

SQL將首先評估所有AND語句，然後評估OR語句;如果你把他們周圍的括號，你可能會得到期望的結果：

SELECT * FROM workshops 
WHERE (workshop_zipcode LIKE '75___' 
OR workshop_zipcode LIKE '77___') 
AND workshop_category = 14 
AND active = 1 
AND workshop_date >= NOW() 
ORDER BY workshop_date ASC 

這將檢查車間郵編，然後你的標準的其餘部分。