Question

如果组中至少有一个值符合条件，如何创建组？

以下是数据库表test：

的示例

| ID | TYPE | COLOR |
|====|======|=======|
|  1 |    1 |     R |
|  2 |    1 |     B |
|  3 |    1 |     G |
|  4 |    2 |     B |
|  5 |    2 |     G |
|  6 |    3 |     G |

我需要选择具有多个行的所有TYPE值，并且该TYPE中至少有一个COLOR为G.

所以伪选择看起来像这样：

  select TYPE 
    from test
group by TYPE
  having count(*) > 1
     and count(COLOR = 'G') > 0

Answer 1

根据OP的修改要求：

select   type
from     test
group by type
having   count(*) > 1 and count(case when color = 'G' then 0 end) > 0
;

Answer 2

count仅计算非null值。将两个必需条件都包含在一个中的巧妙技巧是计算返回G的内容的case表达式的不同数量以及其他任何值的其他值：

SELECT   type
FROM     test
GROUP BY type
HAVING   COUNT(DISTINCT CASE color WHEN 'G' THEN 1 ELSE 2 END) = 2

Answer 3

您可以在计数（颜色）上使用内连接

 select t1.type 
 from test  t1
 inner join (
     select type, count(color)
     from test
     where  type in (select  type from test where color='G' )
     group by type
 ) t2 on t1.type = t2.type
 group by t1.type 
 having count(*) > 1

或以最简单的方式

   select t1.type 
   from test  t1
   inner join  test t2 on t1.type = t2.type and t2.color = 'G'
   group by t1.type 
   having count(*) > 1

如果组中至少有一个值符合条件

3 个答案: