>1. How to increase the char(4) to Char(5) in field employee number in SQL script ? ALTER COLUMN command is ok or not.

You can do that with ALTER TABLE ... ALTER COLUMN


>2. How to add field at the end of the Orders table in SQL script too ?
>may be ALTER Column command is the right command to do it or not
>
>Orderstable has 2 fields now :
>orderid
>productid
>
>the new field : quantity
>
>with SQL script

ALTER TABLE Orders ADD quantity ...

You can do those modifications in Enterprise Manger and instead of applying them, generate script to see how it is done.