I managed to solve the problem:
First
string alterSQL = "ALTER TABLE <totable> ADD <column> NVARCHAR(5) ";
Now comes the update
string qryMove ="UPDATE <totable> SET <column> = (SELECT <column> FROM <fromtable> WHERE <fromtable.keycolumn> = <totable.keycolumn>)";
After update I can remove the old column från the table:
string strDelColumn = "ALTER TABLE <fromtable> DROP COLUMN <column>;
Execute the SQL queries
Functions Execute = new Functions();
Execute.MySqlCommand(alterSQL, connCopy);
Execute.MySqlCommand(qryMove, connCopy);
Execute.MySqlCommand(strDelColumn, connCopy);
That's all.
Vidor