SQL查詢的WHERE子句

我有這條線在我的SQL查詢：SQL查詢的WHERE子句

WHERE client = $id 
    AND (isinvoiced = 0) OR (isinvoiced = 1 and isrecurring = 1)

其得到更多的結果，比我期待的。不過，如果我這樣寫：

WHERE client = $id 
    AND (isinvoiced = 0) OR (isinvoiced = 1 and isrecurring = 1 and client = $id)

然後它得到我想要的結果，但這是寫這個最好的方法嗎？我只是不想再遇到這個代碼的更多問題。

來源

2012-04-23 user979331

Google for [Distributivity rewrite rules]（http://en.wikipedia.org/wiki/Distributivity）。 – onedaywhen 2012-04-23 15:32:37

你確定你明白'a AND b OR c'和'a AND（b OR c）'的區別嗎？你的例子更清楚地寫成'（a AND b）或c'，而不是你真正想要的。 – MatBailie 2012-04-23 15:38:08

圍繞整個AND子句，您需要多一組()。這說明client = $id必須是真實的，其他條件中的任何一個也必須是我= isinvoiced = 0或isinvoiced = 1 and isrecurring = 1的組合。

WHERE client = $id 
    AND ((isinvoiced = 0) OR (isinvoiced = 1 and isrecurring = 1))

來源

2012-04-23 15:26:12

完美的邁克爾，多數民衆贊成我正在尋找，再次感謝......我會投票給你的答案，當它讓我。 – user979331 2012-04-23 15:27:34

如果'isinvoiced = 1'與'isinvoiced = 0'正好相反（即'isinvoiced'不能包含其他值，也不包含'NULL'），則可以進一步簡化：WHERE client = $ id AND isinvoiced = 0或isrecurring = 1）'。 – 2012-04-24 05:06:57

where client = $id 
    and (
     isinvoiced = 0 
     or (
      isinvoiced = 1 
      and isrecurring = 1 
      ) 
     )

來源

2012-04-23 15:26:54 RedFilter

-1

如果where子句

remove -> WHERE client = $id

，只是有

WHERE (isinvoiced = 0) OR (isinvoiced = 1 and isrecurring = 1 and client = $id)

這是否讓你的結果你想刪除初始？

來源

2012-04-23 15:27:12 Robert

OP要始終匹配「客戶端」。看到接受的答案。 – Ben 2012-04-23 21:35:08

添加括號在你AND條款：

WHERE client = $id 
    AND ((isinvoiced = 0) OR (isinvoiced = 1 and isrecurring = 1))

來源

2012-04-23 15:27:12 Oded

你想要的是這樣的：

WHERE client = $id AND ((isinvoiced = 0) OR (isinvoiced = 1 and isrecurring = 1))

如果你不把多餘的blaquets它將使一個OR與客戶restiction並給出更多結果。

來源

2012-04-23 15:27:18

關於SQL，您應該旨在編寫搜索條件conjunctive normal form（「AND條款的一個系列」）。有各種rewrite rules來協助這一點。

的distributive rewrite law在這種情況下有用即

(P AND Q) OR R <=> (P OR R) AND (Q OR R)

你的情況：

(isinvoiced = 0) OR (isinvoiced = 1 AND isrecurring = 1)

可改寫爲：

(isinvoiced = 0 OR isinvoiced = 1) AND (isinvoiced = 0 OR isrecurring = 1)

因此，無需笨重的整個搜索條件parens：

.... 
WHERE client = $id 
     AND (isinvoiced = 0 OR isinvoiced = 1) 
     AND (isinvoiced = 0 OR isrecurring = 1);

來源

2012-04-24 08:28:15 onedaywhen

SQL查詢的WHERE子句

回答

相關問題