Question

我有代码，如果有重复，那么它会说“用户名已经存在”。但是，它继续记录我的数据库中的firstname，lastname和middlename等其他数据（username除外）。如果一个数据有重复，如何阻止它记录其他值？

    Try
      Const SQLStatement As String = "START TRANSACTION; INSERT INTO people(Firstname, Middlename, Lastname) VALUES ( @p0, @p1, @p2); 

INSERT account(uname, pass, type) VALUES( @p3, @p4,@p5); COMMIT;"

                Using connection As New MySqlConnection()
                   connection.ConnectionString = ServerString
                    Dim command As New MySqlCommand(SQLStatement, connection)
                    command.Parameters.AddWithValue("@p0", firstname.Value)
                    command.Parameters.AddWithValue("@p1", middlename.Value)
                    command.Parameters.AddWithValue("@p2", lastname.Value)
                    command.Parameters.AddWithValue("@p3", username.Value)
                    command.Parameters.AddWithValue("@p4", password.Value)
                    command.Parameters.AddWithValue("@p5", type.Value)
                    connection.Open()
                    command.ExecuteNonQuery()
                End Using
                lblALabel.Text = "Successfully Registered!"
                firstname.Value = ""
                middlename.Value = ""
                lastname.Value = ""
                username.Value = ""
                password.Value = ""
            Catch ex As Exception
                lblALabel.Text = "Username is taken"
            End Try

Answer 1

试试这个......
它将首先检查“UserName”，如果不存在，则会插入您的数据。

  Try
       Const SQLStatement As String = "IF NOT EXISTS(SELECT * FROM ACCOUNT WHERE UNAME=@P3) 
       BEGIN 
          START TRANSACTION; 
            INSERT INTO people(Firstname, Middlename, Lastname) VALUES ( @p0, @p1, @p2);
            INSERT account(uname, pass, type) VALUES( @p3, @p4,@p5); 
          COMMIT; 
       END"
      .......
      .......
   Catch ex As Exception
      lblALabel.Text = "Username is taken"
   End Try

尝试捕获录制数据

1 个答案: