Re: auto-increment column

[Robert Buckley <robertdbuckley@xxxxxxxxx>]

Thanks for the replies,

I have one question regarding this comment...

"You also need to add a DEFAULT _expression_ and optionally

make the sequence owned by the column:"

What difference does it make if a table "owns" a sequence of not?...does this contraint the use of the sequence to ONLY that one table?

The sequence will only be used to auto-increment the id column in order to have an automatic primary key. Could I then somehow use the sequence for all tables which need this?

yours,

Rob

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Von: Boszormenyi Zoltan <zb@xxxxxxxxxxx>
An: pgsql-general@xxxxxxxxxxxxxx
Gesendet: 13:43 Dienstag, 4.Oktober 2011
Betreff: Re: auto-increment column

2011-10-04 13:30 keltezéssel, Robert Buckley írta:

Hi,

I have a column in a table called hist_id with the datatype "integer". When I created the table I assigned this column the primary key constraint but didn´t make it an auto-increment column.

How could I do this to an the already existing column?

I have created the sequence with the following command but don´t know how to change the existing column to auto-increment.

$ create sequence hist_id_seq;

You also need to add a DEFAULT _expression_ and optionally
make the sequence owned by the column:

ALTER TABLE tablename ALTER COLUMN hist_id SET DEFAULT nextval('hist_id_seq');
ALTER SEQUENCE hist_id_seq OWNED BY tablename.hist_id;

The "ALTER SEQUENCE ... OWNED BY ..." will make the sequence
automatically dropped if this column or table is dropped.

thanks for any help,

Rob

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