Question

这是一种挑战。预期的产量，所有水果都来自ny或ak状态，如果商标好=价格10和坏=价格20和OK =价格40.那么，来自纽约州的苹果，标记好坏匹配价格10和20，和苹果没有标记OK行，所以无需比较。香蕉标记坏=价格20，但OK价格不等于40，所以我将排除香蕉。梨匹配OK =价格40和州= ny并且没有好的和坏的标记行。因此，我的输出应该是苹果和梨。我该怎么做？

<?php
/*
fruit  state  price   mark
apple   ny      10    good
apple   ny      20    bad
banana  ny      20    bad
banana  ny      30    OK
pear    ny      40    OK
berry   pa      10    good
*/

/*this is my best query but fail to do what I expected*/
SELECT fruit FROM table WHERE state IN ('ny','ak')  AND mark IN ('good',  'bad', 'OK') AND price IN ( '10','20','40') GROUP BY fruit	
?>

Answer 1

你应该在哪里和/或条件

你应该使用一对不在

select distinct fruit from  my_table 
where fruit not in (select distinct fruit from my_table 
     where (mark, price) not in (select 'good', 10 from dual 
                            union 
                            select 'bad, 20 from dual
                            union 
                            select 'OK', 40 from dual))
state IN ('ny','ak') ;

Answer 2

可能返回的潜在水果列表，因为一行符合规范：

SELECT t.fruit
  FROM `table` t
 WHERE t.state IN ('ny','ak')
   AND ( ( t.mark = 'good' AND t.price = 10 )
      OR ( t.mark = 'bad'  AND t.price = 20 )
      OR ( t.mark = 'OK'   AND t.price = 40 )
       )
 GROUP BY t.fruit

我们不想返回的水果列表，因为有一行不符合规范：

SELECT t.fruit
  FROM `table` t
 WHERE t.state IN ('ny','ak')
   AND NOT ( t.mark = 'good' AND t.price = 10 )
   AND NOT ( t.mark = 'bad'  AND t.price = 20 )
   AND NOT ( t.mark = 'OK'   AND t.price = 40 )
 GROUP BY t.fruit

请注意，这还包括mark列的值不是good，bad或OK的行。如果我们想忽略具有其他mark值的行，那么我们将添加...

   AND t.mark IN ('good','bad','OK')

这给了我们两套。我们可以将它们与反连接操作结合起来。作为一个示例，如果我们有表fruit_to_include和fruit_to_exclude ...

SELECT i.fruit
  FROM fruit_to_include i
  LEFT
  JOIN fruit_to_exclude e
    ON e.fruit = i.fruit
 WHERE e.fruit IS NULL
 ORDER BY i.fruit

我们可以使用内嵌视图替换这些占位符表名称，使用提供水果的查询和要排除的水果。这里唯一的区别是用（MySQL所指的）派生表替换虚拟表名。

SELECT i.fruit
  FROM -- fruit_to_include
       ( SELECT t.fruit
           FROM `table` t
          WHERE t.state IN ('ny','ak')
            AND ( ( t.mark = 'good' AND t.price = 10 )
               OR ( t.mark = 'bad'  AND t.price = 20 )
               OR ( t.mark = 'OK'   AND t.price = 40 )
                )
          GROUP BY t.fruit
       ) i
  LEFT
  JOIN -- fruit_to_exclude
       ( SELECT r.fruit
           FROM `table` r
          WHERE r.state IN ('ny','ak')
            AND r.mark IN ('good','bad','OK')
            AND NOT ( r.mark = 'good' AND r.price = 10 )
            AND NOT ( r.mark = 'bad'  AND r.price = 20 )
            AND NOT ( r.mark = 'OK'   AND r.price = 40 )
          GROUP BY r.fruit
       ) e
    ON e.fruit = i.fruit
 WHERE e.fruit IS NULL
 ORDER BY i.fruit

基于这个表，如何获得预期的输出mysql php？

2 个答案: