Question

我已经在VB上使用了这个：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim con As New SqlConnection
Dim cmd As New SqlCommand

Try
con.ConnectionString = "Server=SISTEMAS\SQLEXPRESS;Database=UPC;Trusted_Connection=Yes" 'Coneccion a la base de datos'"
con.Open()
cmd.Connection = con
cmd = New SqlCommand("SELECT * FROM UPC_Table WHERE UPCNumber='" & TextBox1.Text & "' AND Description= '" & TextBox2.Text & "'", con)
Dim numerorecord As Int32 = cmd.ExecuteScalar

If numerorecord > 0 Then
MsgBox("NUMERO DE UPC YA EXISTE")
Else
cmd.CommandText = "INSERT INTO UPC_Table (UPCNumber, Description) VALUES ('" & TextBox1.Text & "','" & TextBox2.Text & "')" 'Codigo para insertar UPC del text box a la base de datos'
cmd.ExecuteNonQuery()
MessageBox.Show("UPC Entrado")
End If


Catch ex As Exception
MessageBox.Show("Error..." & ex.Message, "Inserta el Record")
Finally
con.Close()
End Try

End Sub

我想在第一个消息框中为我带来一条SQL记录。例如：

我们在upc文本框上输入upc＃123456然后再次输入一个消息框，说upc＃123456属于让我们说KETCHUP（这来自SQL数据库）

Answer 1

我会做一些改变来实现这个目标：

1）仅从数据库中返回所需的列（在我的示例中，将myFieldName更改为列的名称）

2）从查询中返回一个对象，检查对象是否有值并进行相应的处理。

修订后的代码如下。

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Dim con As New SqlConnection
        Dim cmd As New SqlCommand

        Try
            con.ConnectionString = "Server=SISTEMAS\SQLEXPRESS;Database=UPC;Trusted_Connection=Yes" 'Coneccion a la base de datos'"
            con.Open()
            cmd.Connection = con
            cmd = New SqlCommand("SELECT myFieldName FROM UPC_Table WHERE UPCNumber='" & TextBox1.Text & "' AND Description= '" & TextBox2.Text & "'", con)

            Dim val As Object = cmd.ExecuteScalar()

            If val Is Nothing Then
                cmd.CommandText = "INSERT INTO UPC_Table (UPCNumber, Description) VALUES ('" & TextBox1.Text & "','" & TextBox2.Text & "')" 'Codigo para insertar UPC del text box a la base de datos'
                cmd.ExecuteNonQuery()
                MessageBox.Show("UPC Entrado")
            Else
                MsgBox("The UPC is" & val)
            End If


        Catch ex As Exception
            MessageBox.Show("Error..." & ex.Message, "Inserta el Record")
        Finally
            con.Close()
        End Try

    End Sub

如何在消息框中显示SQL数据库中的字段

1 个答案: