Question

查询两个表的总和

我有一个交易表和一张付款表。我需要在Trans Table和Payment Table上获得总金额，并且它必须由TransID分组。我希望有人可以帮我找到正确的sql语句。

我尝试了下面的sql但是Trans Table上的金额总和将乘以Payment表上相同TransID的记录数。

-> Select Trans.TransID, sum(Trans.Amount), sum(Payment.Amount) 
   from Trans
   Left Join Payment on Payment.TransID = Trans.TransID

我也尝试了下面的sql，但与上面的sql语句相比，处理时间更长。

-> Select TD.TransID, TD.Amt, PD.paid 
   from
   (
       Select Trans.TransID, Sum(Trans.Amount) AS Amt 
       from Trans Group By Trans.TransID
   ) AS TD 
   Left Join
   (
       Select Payment.TransID, sum(Payment.Amount) AS Paid 
       from payment 
       Group by Payment.TransID
   ) AS PD On PD.TransID = TD.TransID

Trans Table

TransID |   Amount   
T1      |   10    
T2      |   15    
T3      |   12    
T4      |   20    
T5      |   11    
T1      |   15    
T5      |   14


----------

付款表

TransID |   Amount    
T1      |   5    
T3      |   10          
T1      |   3    
T2      |   5    
T5      |   10


----------

我需要的查询结果应该是这样的：

TransID  |  Amount  |   Paid    
T1       |  25      |   8    
T2       |  15      |   5    
T3       |  12      |   10    
T4       |  20      |   0   
T5       |  25      |   10

Answer 1

您可以使用两个不同的查询，一个对所有Amounts进行求和（并将Paid列设置为0），另一个对所有Paid值求和（并将Amount列设置为0）并使用UNION ALL查询和SUM进行组合结果：

SELECT TransID, SUM(Amount) AS Amount, SUM(Paid) AS Paid
FROM (
  SELECT TransID, SUM(Amount) AS Amount, 0 AS Paid
  FROM Trans
  GROUP BY TransID
  UNION ALL
  SELECT TransID, 0 AS Amount, SUM(Amount) AS Paid
  FROM Payment
  GROUP BY TransID
) s
GROUP BY TransID

请查看小提琴here。

Answer 2

就处理时间而言，如果您有“付款（转账，金额）

的索引，则以下内容可能最快

SELECT t.TransId, t.Amount,
       (SELECT SUM(p.Amount)
        FROM Payment p
        WHERE p.TransId = t.TransId
       ) as Paid
FROM (SELECT t.TransID, SUM(t.Amount) AS Amount
      FROM Trans t
      GROUP BY t.TransID
     ) t;

MySQL将利用相关子查询的索引，该索引应该比三个group by查询更快。

查询将两个表相加

2 个答案: