为什么左右连接会忽略查询中的某些值？

Question

我有一个包含 3 列的表和这些值：

col1   col2   col3
-------------------
  1      2      8
  1      3      5
  1     10     15
  2      4      6
  2      9      7
  3      5      6

我加入查询 LEFT JOIN 和 RIGHT JOIN 对每个数字 (MS-ACCESS) 的分组和计数查询。

SELECT Col1 AS Num, t1.CON1, t2.CON2, t3.CON3
        FROM
           (((SELECT col1, COUNT(col1) AS CON1 FROM table GROUP BY col1) AS t1
              LEFT JOIN (SELECT col2, COUNT(col2) AS CON2 FROM table GROUP BY col2) AS t2
                         ON t1.col1 = t2.col2)
              LEFT JOIN (SELECT col3, COUNT(col3) AS CON3 FROM table GROUP BY col3) AS t3
                         ON t2.col2 = t3.col3)
        UNION
        SELECT col3 AS Num, t1.CON1, t2.CON2, t3.CON3
        FROM
           (((SELECT col1, COUNT(col1) AS CON1 FROM table GROUP BY col1) AS t1
              RIGHT JOIN (SELECT col2, COUNT(col2) AS CON2 FROM table GROUP BY col2) AS t2
                          ON t1.col1 = t2.col2)
              RIGHT JOIN (SELECT col3, COUNT(col3) AS CON3 FROM table GROUP BY col3) AS t3
                          ON t2.col1 = t3.col3)

结果如下：

Num  CON1  CON2  CON3
--------------------------
  1    3      
  2    2     1
  3    1     1
  5          1     1
  6                2
  7                1
  8                1
 15                1

但是此查询忽略了表第 2 列中的值计数

Num    CON2
--------------- 
   4       1
   9       1
  10       1

我的查询中缺少什么？

Answer 1

如果要计算每列中的每个值和次数，请使用union all拆分数据，然后group by ：

select num, sum(col1), sum(col2), sum(col3)
from ((select col1 as num, 1 as col1, 0 as col2, 0 as col3
       from t
      ) union all
      (select col2 as num, 0 as col1, 1 as col2, 0 as col3
       from t
      ) union all
      (select col3 as num, 0 as col1, 0 as col2, 1 as col3
       from t
      )
     ) as x
group by num
order by num;

Answer 2

这给出了正确的总数，但我不知道如何总结结果（例如，它列出了 3 次）......

(
        (SELECT col1 as num, COUNT(col1) AS CON1, null as CON2, null as CON3  FROM mytable t1
          LEFT JOIN (SELECT col2, COUNT(col2) AS CON2 FROM mytable GROUP BY col2)  t2
                     ON t1.col1 = t2.col2
          LEFT JOIN (SELECT col3, COUNT(col3) AS CON3 FROM mytable GROUP BY col3)  t3
                     ON t2.col2 = t3.col3
        GROUP BY t1.col1)

        UNION

       (SELECT col2 as num, null as CON1, COUNT(col2) AS CON2, null as CON3  FROM mytable t4
          left JOIN (SELECT col1, COUNT(col1) AS CON1 FROM mytable GROUP BY col1)  t5
                      ON t4.col2 = t5.col1
          left JOIN (SELECT col3, COUNT(col3) AS CON3 FROM mytable GROUP BY col3)  t6
                      ON t4.col2 = t6.col3

        GROUP BY t4.col2)

        UNION

         (SELECT col3 as num, null as CON1, null as CON2, COUNT(col3) AS CON3 FROM mytable t7
          left JOIN (SELECT col1, COUNT(col1) AS CON1 FROM mytable GROUP BY col1)  t8
                      ON t7.col3 = t8.col1
          left JOIN (SELECT col2, COUNT(col2) AS CON3 FROM mytable GROUP BY col2)  t9
                      ON t7.col3 = t9.col2

        GROUP BY t7.col3)
        )

结果：

num     CON1    CON2    CON3
1        3      
2                1  
2        2      
3                1  
3        1  
4                1
5                        1
5                1  
6                        2
7                        1
8                        1
9                1  
10               1  
15                       1

... 任何人？

SQL 测试： https://sqltest.net/#979886