Question

我有两个疑问。首先将返回10行，第二次查询将返回2行。但是，当我将查询合并为一个时，它仍然只返回10行。

以下是我的疑问。

SELECT * 
FROM   contentmsg 
WHERE  apmc_id = '5284a327e4b0bc1eaf3d118e' 
       AND commodity_id IS NULL 
       AND lang_id IS NULL 
       AND date < '2014-07-05 09:25' 
       AND date >= '2014-06-13 14:17:22' 
ORDER  BY -date 
LIMIT  0, 10

输出两条记录

SELECT * 
FROM   contentmsg 
WHERE  apmc_id = '5284a327e4b0bc1eaf3d118e' 
       AND commodity_id IN ( '5226d086e4b05917e5ca33bc', '5226d086e4b05917e5ca33b6', '5226d086e4b05917e5ca33d9', '5226d086e4b05917e5ca3408',
                             '5226d086e4b05917e5ca33e1', '5226d086e4b05917e5ca33ec', '5226d086e4b05917e5ca33b4' )
       AND lang_id = '51fb5a2ee4b0e18f7f89ecc8' 
       AND date < '2014-07-05 09:25' 
       AND date >= '2014-06-13 14:17:22' 
ORDER  BY date 
LIMIT  0, 10

输出 10条记录..

这些查询之间的唯一区别是，goods_id设置为null，并且在第一个查询中将lang_id设置为null。

我已尝试使用此查询，其中添加了“OR”

SELECT * 
FROM   contentmsg 
WHERE  apmc_id = '5284a327e4b0bc1eaf3d118e' 
       AND commodity_id IS NULL 
        OR commodity_id IN ( '5226d086e4b05917e5ca33bc', '5226d086e4b05917e5ca33b6', '5226d086e4b05917e5ca33d9', '5226d086e4b05917e5ca3408',
                             '5226d086e4b05917e5ca33e1', '5226d086e4b05917e5ca33ec', '5226d086e4b05917e5ca33b4' )
           AND lang_id IS NULL 
        OR lang_id = '51fb5a2ee4b0e18f7f89ecc8' 
           AND date < '2014-07-05 09:25' 
           AND date >= '2014-06-13 14:17:22' 
ORDER  BY -date 
LIMIT  0, 10

查询中有错误吗？

Answer 1

您需要注意order of precedence与AND＆amp;在OR之前评估AND个运算符（OR）。要解决此问题，请将操作括在括号中：

SELECT * 
FROM   contentmsg 
WHERE  apmc_id = '5284a327e4b0bc1eaf3d118e' 
       AND ( commodity_id IN ( '5226d086e4b05917e5ca33bc', '5226d086e4b05917e5ca33b6', '5226d086e4b05917e5ca33d9', '5226d086e4b05917e5ca3408',
                               '5226d086e4b05917e5ca33e1', '5226d086e4b05917e5ca33ec', '5226d086e4b05917e5ca33b4' )
             AND lang_id = '51fb5a2ee4b0e18f7f89ecc8' ) 
        OR ( commodity_id IS NULL 
             AND lang_id IS NULL ) 
           AND date < '2014-07-05 09:25' 
           AND date >= '2014-06-13 14:17:22' 
ORDER  BY -date

无法从mysql中将两个查询的结果合二为一

1 个答案: