{CALL sp_update_my_customer(
   {ml o.cust_1st_pk},
   {ml o.cust_2nd_pk},
   {ml o.first_name},
   {ml o.last_name},
   {ml o.nullable_col},
   {ml o.last_modified},
   {ml r.first_name},
   {ml r.last_name},
   {ml r.nullable_col},
   {ml r.last_modified}
)} 
CREATE PROCEDURE sp_update_my_customer(
     @cust_1st_pk        INTEGER,
     @cust_2nd_pk        INTEGER,
     @old_first_name     VARCHAR(100),
     @old_last_name      VARCHAR(100),
     @old_nullable_col   VARCHAR(20),
     @old_last_modified  DATETIME,  
     @new_first_name     VARCHAR(100),
     @new_last_name      VARCHAR(100),
     @new_nullable_col   VARCHAR(20),
     @new_last_modified  DATETIME
) 
BEGIN
DECLARE @current_last_modified DATETIME;
// Detect a conflict by checking the number of rows that are
// affected by the following update. The WHERE clause compares
// old values uploaded from the remote database to current values in
// the consolidated database. If the values match, there is
// no conflict. The COALESCE function returns the first non-
// NULL expression from a list, and is used in this case to
// compare values for a nullable column.


UPDATE my_customer
SET first_name                  = @new_first_name,
 last_name                      = @new_last_name,
 nullable_col                   = @new_nullable_col,
 last_modified                  = @new_last_modified

WHERE cust_1st_pk               = @cust_1st_pk
 AND cust_2nd_pk                = @cust_2nd_pk
 AND first_name                 = @old_first_name
 AND last_name                  = @old_last_name
 AND COALESCE(nullable_col, '') = COALESCE(@old_nullable_col, '')
 AND last_modified              = @old_last_modified;
... 
// Use the @@rowcount global variable to determine
// the number of rows affected by the update. If @@rowcount=0,
// a conflict has occurred. In this example, the database with
// the most recent update wins the conflict. If the consolidated
// database wins the conflict, it retains its current values
// and no action is taken.

IF( @@rowcount = 0 ) THEN
// A conflict has been detected. To resolve it, use business
// logic to determine which values to use, and update the
// consolidated database with the final values.

  SELECT last_modified INTO @current_last_modified
     FROM my_customer WITH( HOLDLOCK )
     WHERE cust_1st_pk=@cust_1st_pk
        AND cust_2nd_pk=@cust_2nd_pk;

     IF( @new_last_modified > @current_last_modified ) THEN
     // The remote database has won the conflict: use the values it
     // uploaded.
  
       UPDATE my_customer
       SET first_name    = @new_first_name,
         last_name     = @new_last_name,
         nullable_col  = @new_nullable_col,
         last_modified = @new_last_modified
       WHERE cust_1st_pk  = @cust_1st_pk
          AND cust_2nd_pk   = @cust_2nd_pk;
       
     END IF;
END IF;
END;