thanks healdem, for your reply, Healdem, I used the query "select * from information_schema.table_constraints", which showed me, the list of all the tables with constraints, and it also had the table which I was targeting to change the field length of. But in the constraint type column that particular table showed unique. all of the other showed primary key, which I didnt know what to do with. Secondly, following the link you provided in your reply, i dropped the constraints some how, and was able to change the length of the field from varchar(4) to varchar(30). But after changing the field length, when I tried to enter more than 4 characters, sql generated an error saying "String or binary data may be truncated. The statement has been terminated."
What should I do? I have no clue what so ever.
I have a backup copy of the database, therefore I can always start with a fresh copy again. But what to do. please enlighten me.