Question

我的查询有问题，通过连接多个表使用sum或count数据，查询结果不匹配，结果成倍增加，在使用连接多个表计算数据时我应该考虑什么，它足以让我困惑

像这样：

我有4个相互连接的表

select T3.series,  
sum(If(Month = 1 and Year = 2013,jumlah,0)) as 'JAN 13', 
sum(If(Month = 2 and Year = 2013,jumlah,0)) as 'FEB 13', 
sum(If(Month = 3 and Year = 2013,jumlah,0)) as 'MAR 13'
From Typemotor T3
LEFT JOIN (
select T.Series,Month(C.Date) as Month,Year(C.Date) as Year,
Count(T.Series) as Jumlah
from 
(select a.Type, a.Date,a.MachineNumber
from 
selling_cash a
left join lokasi b
on a.Showr = b.KodeLokasi
where b.PT = 'PT MERDEKA'
group by a.MachineNumber)
as C
Left Join Typeconvert T2
on C.Type = T2.TypeSystem
Left Join Typemotor T
on T2.TypeConv = T.Type
Group by T.Series,Month,Year ) as R
On R.Series = T3.Series
Group by T3.Series order by T3.Series asc;

结果是：

+--------------------+--------+--------+--------+  
| series             | JAN 13 | FEB 13 | MAR 13 |
+--------------------+--------+--------+--------+
| AUTOMATIC LPM      |  13068 |   9416 |  10648 |
| AUTOMATIC PREMIUM  |    187 |    506 |    330 |
| AUTOMATIC STANDART |  11502 |  12690 |  10206 |
| JUPITER SERIES     |   3584 |   3360 |   3360 |
| LEXAM              |      0 |      0 |      0 |
| MX SERIES          |   3456 |   1664 |   3200 |
| SPORT              |   9620 |   7852 |   7826 |
| VEGA SERIES        |   2808 |   1728 |   1080 |
+--------------------+--------+--------+--------+

结果是

+--------------------+--------+--------+--------+
| series             | JAN 13 | FEB 13 | MAR 13 |
+--------------------+--------+--------+--------+
| AUTOMATIC LPM      |     33 |     28 |     38 |
| AUTOMATIC PREMIUM  |      3 |      9 |      6 |
| AUTOMATIC STANDART |     35 |     41 |     32 |
| JUPITER SERIES     |     22 |     20 |     20 |
| LEXAM              |      0 |      0 |      0 |
| MX SERIES          |     27 |     13 |     25 |
| SPORT              |     80 |     64 |     64 |
| VEGA SERIES        |     13 |      8 |      5 |
+--------------------+--------+--------+--------+

是否有任何建议，指出需要考虑与连接表执行计算/求和以使结果正确？

Answer 1

我不是一个mysql人，但我会对你的查询做一些观察。

首先，我在子句“group by a.MachineNumber”中看不到任何意义，因为此查询不包含聚合函数。

为了清楚起见，我在此重复您的查询：

select T3.series,  
  sum(If(Month = 1 and Year = 2013,jumlah,0)) as 'JAN 13', 
  sum(If(Month = 2 and Year = 2013,jumlah,0)) as 'FEB 13', 
  sum(If(Month = 3 and Year = 2013,jumlah,0)) as 'MAR 13'
From Typemotor T3
  LEFT JOIN (select T.Series, Month(C.Date) as Month, Year(C.Date) as Year, Count(T.Series) as Jumlah
        from (
          select a.Type, a.Date, a.MachineNumber 
          from selling_cash a left join lokasi b on a.Showr = b.KodeLokasi
          where b.PT = 'PT MERDEKA'
          group by a.MachineNumber
        ) as C
          Left Join Typeconvert T2 on C.Type = T2.TypeSystem
          Left Join Typemotor T on T2.TypeConv = T.Type
        Group by T.Series, Month, Year
  ) as R On R.Series = T3.Series
Group by T3.Series 
order by T3.Series asc;

在我看来左翼加入了Typeconvert＆amp; Typemotor都可以移动到C的定义中，并且由于您只对2013年的数据感兴趣，因此可以将这些条件添加到C中的where子句中，此时C需要提供的数据父查询减少为Series，MonthNumber＆amp; Jumlah：

select T3.series,  
  sum(If(Month = 1 and Year = 2013,jumlah,0)) as 'JAN 13', 
  sum(If(Month = 2 and Year = 2013,jumlah,0)) as 'FEB 13', 
  sum(If(Month = 3 and Year = 2013,jumlah,0)) as 'MAR 13'
From Typemotor T3
  LEFT JOIN (
    select Series, MonthNumber, Count(*) as Jumlah
    from (
      select T.Series, Month(a.Date) as MonthNumber 
      from selling_cash a 
        left join lokasi b on a.Showr = b.KodeLokasi
        left Join Typeconvert T2 on C.Type = T2.TypeSystem
        left Join Typemotor T on T2.TypeConv = T.Type
      where b.PT = 'PT MERDEKA' and year(a.Date) = 2013 and month(a.date) <= 3
    ) as C
  Group by Series, MonthNumber
  ) as R On R.Series = T3.Series
Group by T3.Series 
order by T3.Series asc;

但是现在内部查询（R）没有生成您想要的数据？是否还需要总结它？

由于您没有提供您拥有的表定义，以及其中包含的示例数据，我无法回答这个问题。但我认为你需要考虑的是为什么你期望的答案不是你的查询所给出的。

我认为逻辑不太可能是正确的，而不是有一些未知的。

因此我认为最终的查询应该是：

select T3.series,  
  If(MonthNumber = 1,jumlah,0) as 'JAN 13', 
  If(MonthNumber = 2,jumlah,0) as 'FEB 13', 
  If(MonthNumber = 3,jumlah,0) as 'MAR 13'
From Typemotor T3
  LEFT JOIN (
    select Series, MonthNumber, Count(*) as Jumlah
    from (
      select T.Series, Month(a.Date) as MonthNumber 
      from selling_cash a 
        left join lokasi b on a.Showr = b.KodeLokasi
        left Join Typeconvert T2 on C.Type = T2.TypeSystem
        left Join Typemotor T on T2.TypeConv = T.Type
      where b.PT = 'PT MERDEKA' and year(a.Date) = 2013 and month(a.date) <= 3
    ) as C
  Group by Series, MonthNumber
  ) as R On R.Series = T3.Series
order by T3.Series asc;

计算与连接表不匹配

1 个答案: