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Thread: Creating a new column with SERIAL as data type

Creating a new column with SERIAL as data type

From
Kumar S
Date:
Hi group,
 I have an existing table with data loaded. Now I
wanted to create a column with SERIAL data type and
want to make that coulmn values as PRIMARY key.

I did the following:
friends=> alter table friend  add column fr_id serial;
NOTICE:  ALTER TABLE will create implicit sequence
"friend_fr_id_seq" for "serial" column "friend.fr_id"
ERROR:  adding columns with defaults is not
implemented
HINT:  Add the column, then use ALTER TABLE SET
DEFAULT.

Can any one suggest what is wrong here.

Thanks
Kumar




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Re: Creating a new column with SERIAL as data type

From
Tom Lane
Date:
Kumar S <ps_postgres@yahoo.com> writes:
> friends=> alter table friend  add column fr_id serial;
> NOTICE:  ALTER TABLE will create implicit sequence "friend_fr_id_seq" for "serial" column "friend.fr_id"
> ERROR:  adding columns with defaults is not implemented
> HINT:  Add the column, then use ALTER TABLE SET DEFAULT.

> Can any one suggest what is wrong here.

Just what it says: adding columns with defaults is not implemented.
(It is implemented in 8.0, but that won't help you today.)  You can
do it by hand:

create sequence friend_fr_id_seq;
alter table friend add column fr_id int;
update friend set fr_id = nextval('friend_fr_id_seq');
alter table friend alter column fr_id set default nextval('friend_fr_id_seq');

This isn't an exact substitute since the sequence will appear as
a standalone object and not be hidden behind the "serial" column,
but it's functionally equivalent.

            regards, tom lane

Re: Creating a new column with SERIAL as data type

From
Kumar S
Date:
Thank you very much Mr. Lane.
It worked.
Would you mind explaining the code that you sent.
I would appreciate and curious to learn in fact the
meaning of the pg/pl sql statements.
thank you.
Kumar.


--- Tom Lane <tgl@sss.pgh.pa.us> wrote:

> Kumar S <ps_postgres@yahoo.com> writes:
> > friends=> alter table friend  add column fr_id
> serial;
> > NOTICE:  ALTER TABLE will create implicit sequence
> "friend_fr_id_seq" for "serial" column
> "friend.fr_id"
> > ERROR:  adding columns with defaults is not
> implemented
> > HINT:  Add the column, then use ALTER TABLE SET
> DEFAULT.
>
> > Can any one suggest what is wrong here.
>
> Just what it says: adding columns with defaults is
> not implemented.
> (It is implemented in 8.0, but that won't help you
> today.)  You can
> do it by hand:
>
> create sequence friend_fr_id_seq;
> alter table friend add column fr_id int;
> update friend set fr_id =
> nextval('friend_fr_id_seq');
> alter table friend alter column fr_id set default
> nextval('friend_fr_id_seq');
>
> This isn't an exact substitute since the sequence
> will appear as
> a standalone object and not be hidden behind the
> "serial" column,
> but it's functionally equivalent.
>
>             regards, tom lane
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 7: don't forget to increase your free space map
> settings
>




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