使用内部联接执行SQL更新

Question

I am trying to update a field in the user table using an inner join with another table, but it does not seem to be working. I am using the code below:

        SqlCommand cmd = new SqlCommand("UPDATE U SET User.firstname = @Firstname FROM dbo.User AS U INNER JOIN dbo.Driver AS D ON U.userid = D.driverid WHERE D.driverid = @Driverid");
        cmd.CommandType = CommandType.Text;
        cmd.Connection = conn;
        cmd.Parameters.Add("@Firstname", SqlDbType.VarChar, 50).Value = firstname;
        cmd.Parameters.Add("@Driverid", SqlDbType.VarChar, 50).Value = driverid;
        conn.Open();
        cmd.ExecuteNonQuery();

SQL:

UPDATE
  U 
SET 
  User.firstname = @Firstname 
FROM 
  dbo.User AS U 
  INNER JOIN dbo.Driver AS D ON 
    U.userid = D.driverid 
WHERE
  D.driverid = @Driverid

I am getting the following error:

System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.Data.SqlClient.SqlException: Incorrect syntax near the keyword 'User'

Where could I be going wrong? Thanks

Answer 1

The table User is defined/aliased as U in your selecting section, so thus reference it as U in the update fields list:

EDITED : Added square brackets around User which seems to be a reserved SQL keyword.

UPDATE
  U 
SET 
  U.firstname = @Firstname 
FROM 
  dbo.[User] AS U 
  INNER JOIN dbo.Driver AS D ON 
    U.userid = D.driverid 
WHERE
  D.driverid = @Driverid