Question

我有一个查询，我想计算3列s，s2和s3的值并使用Group By列的值？

到目前为止，我已经制作了这个db-fiddle

这会给我输出

1 - count 3  
2 - count 3  
4 - count 4

这几乎是正确的，但我也想包含正确的Where子句，因此计数将仅在season ='2018/2019'并且round = 34的地方。

所需的输出必须是：

1 - count 3  
2 - count 2  
4 - count 2

有什么主意如何编辑此查询，以便Where子句可以在计数值中起作用？

亲切的问候，

Arie

Answer 1

您必须扩展联合查询以包括季节和舍入并在where子句中添加条件：

SELECT t.s, COUNT(*) as count FROM (
    SELECT s, season, round FROM tablename UNION all
    SELECT s2, season, round FROM tablename UNION all
    SELECT s3, season, round FROM tablename
) as t 
WHERE 
  t.s IN (
    SELECT s FROM tablename
    WHERE season = '2018/2019' 
      AND round = 34
      AND s is not null
  )
  AND t.season = '2018/2019' 
  AND t.round = 34
  AND t.s is not null
GROUP BY t.s
ORDER BY count DESC, t.s

请参见demo。
结果：

| s   | count |
| --- | ----- |
| 1   | 3     |
| 2   | 2     |
| 4   | 2     |

Answer 2

您应该过滤并集中每个表的行

SELECT t.s, COUNT(*) as count FROM (
SELECT s 
FROM tablename 
WHERE season = '2018/2019'  and round = 34
UNION all
SELECT s2 
FROM tablename 
WHERE season = '2018/2019' and round = 34
UNION all
SELECT s3 
FROM tablename
WHERE season = '2018/2019' and round = 34
) as t 
GROUP BY t.s
ORDER BY count DESC

使用“分组依据”和“全部合并”计数多个列？

2 个答案: