Question

所以我有一张桌子dpgift。我需要根据表格生成24种不同的“统计数据”（计数和与过滤器的总和）。

下面应该生成前三列。

select a.lc as listCode, a.c, NVL(b.c,0), NVL(c.c,0)
    FROM (select list_code as lc, count(donor) as c
              FROM dpgift 
              group by list_code) a
        LEFT JOIN (select list_code as lc, count(donor) as c
                       FROM dpgift
                       WHERE dpgift.rectype="P" 
                       group by list_code) b
        LEFT JOIN (select list_code as lc, count(donor) as c
                       FROM dpgift
                       WHERE dpgift.rectype="G" 
                       group by list_code) c
            ON b.lc = c.lc 
            ON a.lc = b.lc

这几乎可以正常工作但是我的连接出了问题。第三列（c.c）只有b.c不为空的值。

有人可以告诉我出了什么问题吗？

顺便说一句，我在VFP工作，但是sql似乎非常标准。

编辑：好的，这是我得到的输出

listcode  c    exp_3 Exp_4
482       14   0     0
483       2    0     0
499       852  1     857
....

应该是：

listcode  c    exp_3 Exp_4
482       14   0     14
483       2    0     2
499       852  1     857
....

Answer 1

这个版本应该能够产生你想要的东西。

SELECT list_code,
       COUNT(donor),
       SUM(CASE WHEN rectype = 'P' THEN 1 ELSE 0 END) AS Pcount,
       SUM(CASE WHEN rectype = 'G' THEN 1 ELSE 0 END) AS Gcount
    FROM dpgift
    GROUP BY list_code

SQL多个连接在同一个表上

1 个答案: