將查詢的值賦予變量

Question

幫助，我將SQL Server用作我的數據庫，而我的後端是VB.NET。

我要分配給此查詢的值：

SELECT sum(productPrice) from cartTbl 

給一個變量，然後給值到一個名爲totalPrice文本框。

我該如何執行此操作？先謝謝你！

Answer 1

如果使用ADO.NET

Public Function GetProductPrice() As Integer 
    Dim ProdPrice As Int32 = 0 
    Dim sql As String = "SELECT sum(productPrice) from cartTbl" 

    Using conn As New SqlConnection(connString) 
     Dim cmd As New SqlCommand(sql, conn) 
     Try 
      conn.Open() 
      ProdPrice = Convert.ToInt32(cmd.ExecuteScalar()) 
     Catch ex As Exception 
      Console.WriteLine(ex.Message) 
     End Try 
    End Using 

    Return ProdPrice 
End Function 

您應該使用ExecuteScalar()然後，您可以調用此方法來獲得價格。

Dim prodPrice = GetProductPrice() 

Answer 2

可以使用

SELECT @var1=sum(productPrice) from cartTbl 

Answer 3

使用別名爲您計算列

SELECT sum(productPrice) as prod_sum 
from cartTbl 

然後你就可以像這樣

While dr.Read()  
    totalPrice.Text = dr("prod_sum") 
End While 

Answer 4

讀它，它就是這麼簡單這個，但請閱讀的一些基本信息

Using con = new SqlConnection(.....constring here ....) 
Using cmd = new SqlCommand("SELECT sum(productPrice) from cartTbl", con) 
    con.Open() 
    Dim result = cmd.ExecuteScalar() 
    Console.WriteLine(result) 
End Using 
End Using 

Answer 5

爲了擴大已經取得的說，你可以使用下面的做多一點flexable：

Private Sub Test() 
    'Get/set connection string 
    Me.TextBox1.Text = Me.SQLExecuteScalar(ConnectionString, "SELECT sum(productPrice) FROM cartTbl") 
End Sub 

Public Shared Function SQLExecuteScalar(ByVal ConnectionString As String, ByVal Query As String) As String 
    Dim Result As String = Nothing 

    Dim Exc As Exception = Nothing 

    Using Conn As New SqlClient.SqlConnection(ConnectionString) 
     Try 
      'Open the connection 
      Conn.Open() 

      'Create the SQLCommand 
      Using Cmd As New SqlClient.SqlCommand(Query, Conn) 
       'Create an Object to receive the result 
       Dim Obj As Object = Cmd.ExecuteScalar 

       If (Obj IsNot Nothing) AndAlso (Obj IsNot DBNull.Value) Then 
        'If Obj is not NULL 
        Result = Obj.ToString 
       End If 
      End Using 

     Catch ex As Exception 
      'Save error so we can (if needed) close the connection 
      Exc = ex 

     Finally 
      'Check if connection is closed 
      If Not Conn.State = ConnectionState.Closed Then 
       Conn.Close() 
      End If 

     End Try 

    End Using 

    'Check if any errors where found 
    If Exc IsNot Nothing Then 
     Throw Exc 
    End If 

    Return Result 
End Function