Question

#i have two tables buyers table and sales table#

购买者表

|买家|平衡|

销售表
|买家|销售|购买日期|

我尝试了以下选择查询

Dim connection As OleDbConnection  
Dim adapter As OleDbDataAdapter  
Dim ds As New DataSet  
Dim SQLStr As String  
Dim cmd As OleDbCommand  
connection = New  
OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data 
Source=consignacion.mdb;")    
SQLStr = "SELECT b.buyer as [Buyer],b.balance as 
[Balance],SUM(s.total) as [Sales],  
b.balance+SUM(s.total) as [Total] From buyerdb b  
INNER Join salesdb s on b.buyer=s.buyer  
WHERE s.total Is Not NULL And  
s.buydate =@buydate And  
s.total<>@sales AND  
b.balance> @balance  
GROUP By b.buyer,b.balance"  
SQLStr = "SELECT b.buyer as [Buyer],b.balance as 
[Balance],SUM(s.total) as [Sales],  
b.balance+SUM(s.total) as [Total] From buyerdb b  
INNER Join salesdb s on b.buyer=s.buyer  
WHERE s.total Is Not NULL And  
s.buydate =@buydate And s.total<>@sales AND b.balance> @balance  
GROUP By b.buyer,b.balance"  
cmd = New OleDbCommand(SQLStr, connection)  
cmd.Parameters.AddWithValue("@buydate", Form1.Lbldate2.Text)  
cmd.Parameters.AddWithValue("@balance", 0)  
cmd.Parameters.AddWithValue("@sales", "")

   I expect the output to be  

  buyer   balance  sales   total
  CESS    350 984 1334
  DARWIN  0 345 345
  GLEN    1000 4334 5334
  GLENDA  0 170 170
  JOSE    1000 2240 3240
  LITO    0 120 120
  LOUIE   0 280 280
  TANIS   0 2250 2250
  YOLLY   1500 832 2332
  michael 1500 [null/norecor] 1500
  Dudice   700 [null/norecord] 700


    but the output is

买方余额销售总额

    CESS      350      84      334    
>    DARWIN 0   345 345    
>    GLEN   1000    4334    5334    
>    GLENDA 0   170 170    
>    JOSE   1000    2240    3240    
>    LITO   0   120 120    
>    LOUIE  0   280 280    
>    TANIS  0   2250    2250    
>    YOLLY  1500    832 2332

它没有显示有余额的买方，但是在给定购买日期没有记录的销售额

我已经尽力了。我什至搜索google和youtube，而且似乎无法在我的数据网格视图上获得正确的输出。

Answer 1

如果我要求您向我展示一些不存在的东西，那么您就不能，因为它不存在。数据库中的NULL相同。它们表示不存在某些内容，因此数据库无法向您显示任何内容。

您可以做的是使用ISNULL语句将NULLS替换为实际值。尝试像这样更改您的选择语句：

SELECT b.buyer as [Buyer],b.balance as 
[Balance],SUM(ISNULL(s.total,0)) as [Sales] .........

这会将s.total中的所有NULL替换为0。

无法在2个表的datagridview中的第二列中显示null

1 个答案: