2 Mysql表的總和列Group和subrution pls

Question

有

1.表是。

MgName    MgModel     MgIn 
============================
 CPU    |   i5     |   1
 RAM    |   8GB    |   1 
 BOARD  |   ASUS   |   1
 CPU    |   i5     |   2
 RAM    |   4GB    |   1
 RAM    |   8GB    |   1
 CPU    |   i7     |   1

2.表是。

McName    McModel   McOut
============================
 CPU   |   i5     |   1
 RAM   |   8GB    |   3

3. 我想要相同的組名和相同的模型SUM，然后輸入MgIn-MgOut

=

StckName  StckModel  StckPce 
============================
 CPU    |   i5     |   2
 RAM    |   8GB    |  -1 
 BOARD  |   ASUS   |   1
 CPU    |   i7     |   1
 RAM    |   4GB    |   1

Answer 1

您可以簡單地使用UNION和GROUP BY子句來代替加入：

SELECT t.StckName ,t.StckModel,SUM(t.Mg) as StckPce 
FROM(SELECT MgName as StckName ,MgModel,MgIn as mg as StckModel
     FROM Table1
     UNION ALL
     SELECT McName ,McModel,mcOut*-1
     FROM Table2) t
 GROUP BY t.StckName ,t.StckModel

Answer 2

這是查詢：

SELECT 
t.MgName AS StckName,
t.MgModel AS StckModel,
t.summedValue - IFNULL(Table2.McOut,0) AS StckPce
FROM 
(
  SELECT 
   MgName,
   MgModel,
   SUM(MgIn) summedValue
   FROM Table1
  GROUP BY MgName,MgModel
) t
LEFT JOIN Table2 ON t.MgName = Table2.McName AND t.MgModel = Table2.McModel;

內部查詢獲取每個<MgName,MgModel>對的<MgName,MgModel> 。 然后，此結果與Table2之間的LEFT JOIN將為每個<MgName,MgModel>對獲取相應的McOut值（如果Table2存在）。

最終， summed value與McOut將McOut最終結果。