Hello,

> ALTER COLUMN of ALTER CLAUSE supports modification
> of data type , name and position.
> Eg :
> alter table C1 ALTER COLUMN ID2 {TO ID3 | TYPE
> DOUBLE PRECISION | POSITION 2};
>
> What about changing to NULL/NOT NULL , UNIQUE and
> DEFAULT value. I think like ADD column ALTER column
> can have all such options.

DEFAULT and NULL/NOT NULL as well as changing collation
(if possible) or modifying the current COMPUTED BY clause
sound like useful additions to me.

Do mind, that UNIQUE is not perse a column level constraint,
but rather a table level constraint.

> I agree that it may cause some problems in some
> situation , Eg : When there are some duplicated data
> for an column , setting unique may cause error. But
> still Firebird can throw error in such case.
>
> What do you feel about this suggestion ?
>
> If I am wrong correct me. OR If you agree with this ,
> do I raise it as feature requirement in Firebird
> project?
>
> BTW I am not sure of ANSI standard in this regard ,
> but some other DBs(Oracle , MYSQL , PostgresSQL etc)
> support this functionality. so what I have raised this
> in this forum,

I don't think DDL is covered, but I might be totally wrong
in this regard.

With regards,

Martijn Tonies
Database Workbench - developer tool for InterBase, Firebird, MySQL & MS SQL
Server.
Upscene Productions
http://www.upscene.com