Microsoft SQL Server SELECT语句

Question

我需要帮助从数据库表中检索ReceiptNO列并将其保存到TextBox或Label以供引用。

CODE：

Dim da2 As New SqlDataAdapter 
da2.SelectCommand = New SqlCommand("SELECT RecepitNO FROM Receipt WHERE (PaidFor=@PaidFor AND RegNO=@RegNO)") 
da2.SelectCommand.Parameters.Add("@paidFor", SqlDbType.VarChar).Value = cbMonth.Text 
da2.SelectCommand.Parameters.Add("@RegNO", SqlDbType.Int).Value = lblRegNO.Text 

cn.Open() 
da2.Update(ds.Tables("Receipt")) 
'da2.SelectCommand.ExecuteNonQuery() 
da2.SelectCommand.ExecuteReader() 
cn.Close() 

Answer 1

您需要使用SqlDataReader，然后开始一个循环读取返回的值
此示例将工作假设ReceiptNO是文本字段

cn.Open() 
Dim reader = da2.SelectCommand.ExecuteReader() 
while reader.Read() 
    textBox1.Text = reader("ReceiptNO").ToString() 
End While 

或者，如果您确定您的查询返回零或只有一条记录，并且您只对ReceiptNO字段感兴趣，则可以使用ExecuteScalar

Dim cmd = New SqlCommand("SELECT RecepitNO FROM Receipt WHERE (PaidFor=@PaidFor AND RegNO=@RegNO)") 
cmd.Connection = cn 
cmd.Parameters.Add("@paidFor", SqlDbType.VarChar).Value = cbMonth.Text 
cmd.Parameters.Add("@RegNO", SqlDbType.Int).Value = lblRegNO.Text 
cn.Open() 
Dim result = cmd.ExecuteScalar() 
if result IsNot Nothing Then 
    textBox1.Text = result.ToString() 
End If 

Here the MSDN docs on ExecuteScalar