SQL 多个 where 条件不起作用答案

【问题标题】：SQL multiple where conditions not workingSQL 多个 where 条件不起作用
【发布时间】：2013-12-31 06:53:24
【问题描述】：

我有这 3 个查询，除了 where 语句之外几乎相同：

Insert into t1(f1,f2,f3)
SELECT     t2.f1 AS f1, '' AS f2, t2.f2 AS f2, t3.f3 AS f3)                                                                                    
from  t2 
INNER JOIN t3 ON t2.f1 = t3.f1                       
WHERE     (t2.f4 = 'n') and t2.f5 < '2013-04-01' and t2.f6 in('sss','ttt','ddd')
GROUP BY t2.f4, t2.f5, t2.f6;



Insert into t1(f1,f2,f3)
SELECT     t2.f1 AS f1, '' AS f2, t2.f2 AS f2, t3.f3 AS f3)                                                                                    
from  t2 
INNER JOIN t3 ON t2.f1 = t3.f1                       
WHERE     (t2.f4 = 'n') and t2.f5 > '2013-03-31' and t2.f6 in('sss','ttt','ddd')
GROUP BY t2.f4, t2.f5, t2.f6;


Insert into t1(f1,f2,f3)
SELECT     t2.f1 AS f1, '' AS f2, t2.f2 AS f2, t3.f3 AS f3)                                                                                    
from  t2 
INNER JOIN t3 ON t2.f1 = t3.f1                       
WHERE     (t2.f4 = 'n')  and t2.f6 in('rrr','qqq','yyy')
GROUP BY t2.f4, t2.f5, t2.f6;

我不能像下面的查询一样将它们组合起来，理论上它们是相同的查询吗？因为我完全尝试过这个，当我测试结果时我得到了不同的输出。

   Insert into t1(f1,f2,f3)
   SELECT     t2.f1 AS f1, '' AS f2, t2.f2 AS f2, t3.f3 AS f3)                                                                                    
   from  t2 
   INNER JOIN t3 ON t2.f1 = t3.f1    
   WHERE (t2.f4 = 'n') and (t2.f5 < '2013-04-01' or t2.f5 > '2013-03-31' and t2.f6 in         
   ('sss','ttt','ddd'))  or t2.f6 in ('rrr','ggg','yyy')
    GROUP BY t2.f4, t2.f5, t2.f6;

我也试过这个，但它也不匹配（我几乎只是将前面的每一个 where 语句放在括号中，并在组合语句中添加了一个或）：

 Insert into t1(f1,f2,f3)
   SELECT     t2.f1 AS f1, '' AS f2, t2.f2 AS f2, t3.f3 AS f3)                                                                                    
   from  t2 
   INNER JOIN t3 ON t2.f1 = t3.f1
   WHERE     ((t2.f4 = 'n') and t2.f5 < '2013-04-01' and t2.f6 in('sss','ttt','ddd')) or
((t2.f4 = 'n') and t2.f5 > '2013-03-31' and t2.f6 in('sss','ttt','ddd')) or ((t2.f4 = 'n')  and t2.f6 in('rrr','qqq','yyy'))

【问题讨论】：

标签： mysql sql where-in

【解决方案1】：

它们不是同一个查询，因为 AND 优先于 OR。

所以在你第一次尝试重写时，你有：

(t2.f4 = 'n')
and  (t2.f5 < '2013-04-01' or t2.f5 > '2013-03-31' and t2.f6 in ('sss','ttt','ddd'))
or t2.f6 in ('rrr','ggg','yyy')

满足第三行的任何东西都满足整个 where 子句。

换句话说，你需要在前两行加上括号：

((t2.f4 = 'n')
and  (t2.f5 < '2013-04-01' or t2.f5 > '2013-03-31' and t2.f6 in ('sss','ttt','ddd')))
or t2.f6 in ('rrr','ggg','yyy')

这可能会有所帮助：SQL Logic Operator Precedence: And and Or

【讨论】：

【解决方案2】：

这不行吗？：

Insert into t1(f1,f2,f3)
SELECT     t2.f1 AS f1, '' AS f2, t2.f2 AS f2, t3.f3 AS f3)                                                                                    
from  t2 
 INNER JOIN t3 ON t2.f1 = t3.f1                       
WHERE     ((t2.f4 = 'n') and t2.f5 > '2013-03-31' and t2.f6 in('sss','ttt','ddd'))
OR     ((t2.f4 = 'n') and t2.f5 < '2013-04-01' and t2.f6 in('sss','ttt','ddd'))
OR     ((t2.f4 = 'n')  and t2.f6 in('rrr','qqq','yyy'))
GROUP BY t2.f4, t2.f5, t2.f6;

【讨论】：