Question

我想从表的两个独立列中获取不同值的COUNT。

我的表是：

ID     CR PB      DB CB    
-----------------------------
1      1000       1000
2     60000       1000
3      1000     (NULL)
4   1500000      13000
5     60000      12000
6      1000     (NULL)

预期产出：

CR PB    cnt_crpb   DB CB    cnt_dbcb
1000       3        1000        2
60000      2        13000       1
1500000    1        12000       1

我试图在两个不同的表中分隔列CR PB和DB CB，并使用LEFT JOIN将它们连接起来，但由于MySQL不支持FULL OUTER JOIN，因此不会给出预期的输出。

我也尝试过使用UNION，但结果是行。

任何帮助将不胜感激......

谢谢你。

Answer 1

我认为您需要使用union all执行此操作：

select max(CRPB) as CRPB, max(CRPB_cnt) as CRPB_cnt, max(DBCB) as DBCB, max(DBCB_cnt) as DBCB_cnt
from ((select (@rn1 := @rn1 + 1) as rn, CRPB, count(CRPB) as CRPB_cnt, NULL as DBCB, NULL as DBCB_cnt
       from table t cross join
            (select @rn1 := 0) as vars
       group by CRPB
      ) union all
      (select (@rn2 := @rn2 + 1) as rn, NULL, NULL, DBCB, count(DBCB) as DBCB_cnt
       from table t cross join
            (select @rn2 := 0) as vars
       group by DBCB
      )
     ) x
group by rn;

无论哪个列表最长，都可以保证结果。

Answer 2

请注意，您需要确定哪个列会产生更多结果，即CR PB或DB CB哪个产生最多结果将是您要做的第一个选择然后离开加入另一个。假设两个结果的结果数量不均匀

SELECT `CR PB`, cnt_crpb, `DB CB`, cnt_dbcb
FROM
(   SELECT `CR PB`, COUNT(*) as cnt_crpb, @a := @a + 1 as num_rows_a
    FROM test_table
    CROSS JOIN (SELECT @a := 0 ) temp
    WHERE `CR PB` is not null
    GROUP BY `CR PB`
)t
LEFT JOIN
(   SELECT `DB CB`, COUNT(*) as cnt_dbcb, @b := @b + 1 as num_rows_b
    FROM test_table
    CROSS JOIN (SELECT @b := 0)temp1
    WHERE `DB CB` is not null
    GROUP BY `DB CB`
)t1 ON t1.num_rows_b = t.num_rows_a;

Fiddle Demo

MySQL来自表的两个独立列的不同值的COUNT

2 个答案: