嵌套联合 select 语句

Question

是否可以在不创建临时 table 的情况下对我的 sql SELECT 语句的结果进行分组以在一个语句中求和和分组？我有一个 table 保存贷方帐号和借方帐号的借方和贷方总金额。并为相反的字段置零，我用下面的 union select 语句创建了第一个组页，我需要根据重复的帐户名称对输出求和我可以很容易地得到它还是必须加载它的温度 table？我的 select 声明如下

select  journal_drname  AS ACCNAME, sum(amount) AS DEBT,0 as CREDIT
FROM JOURNAL GROUP BY journal_drname 
 UNION select  journal_crname  AS ACCNAME, 0 as DEBT,sum(amount) AS   
 CREDIT,
 FROM JOURNAL GROUP BY journal_crname

返回数据如下：

ACCNAME      DEBIT     CREDIT
--------   -------     ------
CASH        0           1,000
CASH        900          0
CASH        300          0
BANK        200          0
BANK        400          0

我可以把上面的总结分组如下吗:

ACCNAME      DEBIT     CREDIT
--------   -------     ------
CASH        200          0
BANK        600          0

而且我想把这些要剪的结果加入到上面。

我试图避免使用临时 table，但如果这是唯一可行的方法，我想了解更多有关以这种方式使用临时 table 的信息.

我也试过做一些连接和联合，但不满足条件，我也不知道该怎么做。

Answer 1

如果每个子查询只需要一行，则删除 group by:

select  'CASH' as ACCNAME, sum(amount) AS DEBT, 0 as CREDIT
FROM JOURNAL 
UNION ALL
select  'BANK' as ACCNAME, 0 as DEBT, sum(amount) AS  CREDIT
FROM JOURNAL;

（注意：ACCNAME 值可能会颠倒。）

重要提示：对于此类查询，您应该使用 UNION ALL 而不是 UNION。没有理由承担删除重复项的开销，除非您打算删除重复项。

此外，您的原始查询应该有效，除非 accname 字段中有不寻常的字符。

Answer 2

如您所说，您的查询有效，让我们将您的联合查询称为 table

( ...... ) myTable

然后只需创建一个子查询即可完成最后一步

SELECT ACCNAME,
       CASE WHEN SUM(CREDIT - DEBT) < 0 THEN - SUM(CREDIT - DEBT)
            ELSE 0
       END DEBT,
       CASE WHEN SUM(CREDIT - DEBT) > 0 THEN   SUM(CREDIT - DEBT)
            ELSE 0
       END CREDIT
FROM ( ...... ) myTable
GROUP BY ACCNAME

Answer 3

怎么样：

select ACCNAME, 
    CASE WHEN sum(DEBT)>sum(CREDIT) THEN sum(DEBT)-sum(CREDIT) ELSE 0 AS DEBT, 
    CASE WHEN sum(DEBT)<sum(CREDIT) THEN sum(CREDIT)-sum(DEBT) ELSE 0 AS CREDIT 
FROM (
    select  journal_drname  AS ACCNAME, 
        sum(amount) AS DEBT,
        0 as CREDIT
    FROM JOURNAL GROUP BY journal_drname 
UNION 
    select journal_crname  AS ACCNAME, 
        0 as DEBT,
        sum(amount) AS CREDIT,
 FROM JOURNAL GROUP BY journal_crname
) group by ACCNAME

嵌套联合 select 语句

nested union select statement

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javadb