SQL查询的WHERE子句

我有这条线在我的SQL查询：SQL查询的WHERE子句

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

其得到更多的结果，比我期待的。不过，如果我这样写：

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

然后它得到我想要的结果，但这是写这个最好的方法吗？我只是不想再遇到这个代码的更多问题。

来源

2012-04-23 user979331

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

你确定你明白'a AND b OR c'和'a AND（b OR c）'的区别吗？你的例子更清楚地写成'（a AND b）或c'，而不是你真正想要的。 – MatBailie 2012-04-23 15:38:08

围绕整个AND子句，您需要多一组()。这说明client = $id必须是真实的，其他条件中的任何一个也必须是我= isinvoiced = 0或isinvoiced = 1 and isrecurring = 1的组合。

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

来源

2012-04-23 15:26:12

完美的迈克尔，多数民众赞成我正在寻找，再次感谢......我会投票给你的答案，当它让我。 – user979331 2012-04-23 15:27:34

如果'isinvoiced = 1'与'isinvoiced = 0'正好相反（即'isinvoiced'不能包含其他值，也不包含'NULL'），则可以进一步简化：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 
      ) 
     )

来源

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)

这是否让你的结果你想删除初始？

来源

2012-04-23 15:27:12 Robert

OP要始终匹配“客户端”。看到接受的答案。 – Ben 2012-04-23 21:35:08

添加括号在你AND条款：

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

来源

2012-04-23 15:27:12 Oded

你想要的是这样的：

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

如果你不把多余的blaquets它将使一个OR与客户restiction并给出更多结果。

来源

2012-04-23 15:27:18

关于SQL，您应该旨在编写搜索条件conjunctive normal form（“AND条款的一个系列”）。有各种rewrite rules来协助这一点。

的distributive rewrite law在这种情况下有用即

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

你的情况：

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

可改写为：

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

因此，无需笨重的整个搜索条件parens：

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

来源

2012-04-24 08:28:15 onedaywhen

SQL查询的WHERE子句

回答

相关问题