Re: how to modify a CHECK column-constrait ?

jason_judge_at_my-deja.com wrote in message <7nhh96$92d$1_at_nnrp1.deja.com>...
>
>
>Altering a check constraint requires the old
>constraint to be dropped then replaced, for
>example:
>
>alter table tab1 drop constraint chk1;
>alter table tab1 add constraint chk1 check (col1
>is not null);
>
>This means always giving constraints explicit
>names - if you don't then it is very easy to
>loose them. When you create a un-named check
>constraint in a table create statement, it is
>really defining a table constraint as listed
>above. By keeping the column and constraint
>creationg statements separate is is much easier
>to manage.
>
>As for dropping columns: Oracle 8 can do it, but
>not 7. This is understandable when you look at
>how the data is physically arranged on the disk.
>To drop a column in 7 you must rename the table,
>create a new table then copy the data accross to
>the new table. Having scripted the original
>creation statements the contraints and keys and
>indexes etc can then be recreated on the new
>table.
>
>Oracle is very efficent, stable and fast at what
>is does. In return it asks that the database is
>designed right from the offset - it is not a RAD
>tool like Microsoft Access.
>
>I hope this is useful.
>
>Regards,
>
>Jason

Thanks for the information Jason !

"Live Long and Prosper" - Spock
"And let Wisdom be your Guide" - Spock's brother

Ruud Schmeitz
Universiteit Maastricht Received on Mon Jul 26 1999 - 12:30:47 CDT