Question

我有一个名为＆＃39;记录＆＃39;的mysql表。这种结构： docdate，db，cr，total

和两个查询，如：

comp = comp or function( a, b ) return a < b end

我想在一个sql语句中实现的结果如下：

1. SELECT docdate, SUM(total) as ins FROM records where db='somefilter' AND 'someotherfilters' GROUP BY docdate
2. SELECT docdate, SUM(total) as outs FROM records where cr='somefilter' GROUP BY docdate

任何想法都将受到高度赞赏。 TNX

Answer 1

如果您不介意使用0而不是NULL，则可以在IF内放置SUM，如下所示：

SELECT
    docdate, 
    SUM(IF(db='somefilter' AND 'someotherfilters', total, 0)) as ins,
    SUM(IF(cr='somefilter', total, 0)) as outs
FROM records
GROUP BY docdate

编辑：

如果您确实想要NULL个值，可以将SUM包装在NULLIF语句中

... NULLIF(SUM(...), 0) AS ...

Answer 2

我喜欢SUMIF的答案 - 这是获得相同结果的另一种方法（但是根据要求返回null）

请记住，如果记录表很大（因为两者都需要顺序扫描），这两种方法都会出现可怕的性能问题。这是SQL小提琴http://sqlfiddle.com/#!9/b066c/1

SELECT
  docdate,
  (
    SELECT SUM(total) FROM records r2 WHERE r2.docdate = records.docdate AND r2.field1 = 'Live'
  ) as ins,
  (
    SELECT SUM(total) FROM records r3 WHERE r3.docdate = records.docdate AND r3.field1 = 'Test' AND r3.field2 = 'OK'
  ) as outs
FROM
  records
GROUP BY 1

Answer 3

一种方法是使用UNION，请参阅http://dev.mysql.com/doc/refman/5.7/en/union.html

SELECT docdate, SUM(ins) as ins , SUM(outs) as outs
FROM 
(
    (
    SELECT docdate, SUM(total) as ins , null as outs
    FROM records 
    where db='somefilter' AND 'someotherfilters' 
    GROUP BY docdate
    )
    UNION
    (
    SELECT docdate, null as ins, SUM(total) as outs 
    FROM records 
    where cr='somefilter' GROUP BY docdate
    )
) AS t
GROUP BY docdate;

如何从同一个表中连接两个选择查询结果的mysql

3 个答案: