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Subject: Re: alter table
Date: Wed, 15 Feb 2006 11:56:05 -0800
Message-ID: <144D12D7DD4EC04F99241498BB4EEDCC2207B6@nelson.osl.com>
Thread-Topic: Re[2]: [SQL] alter table
Thread-Index: AcYyaAt9OHIs6WDiR9CGz8uCmmkQSgAADngQ
From: "Owen Jacobson" <ojacobson@osl.com>
To: "Maciej Piekielniak" <piechcio@isb.com.pl>
Cc: <pgsql-sql@postgresql.org>

Maciej Piekielniak wrote:
>=20
> Wednesday, February 15, 2006, 8:31:17 PM, you wrote:
> OJ> Note that prior to 8.0 PostgreSQL does not support=20
> multiple ALTER actions in a single query.  To get an=20
> equivalent effect, wrap separate ALTER TABLE queries in a transaction:
>=20
> OJ> BEGIN;
> OJ> alter table xyz alter column id set default nextval('xyz_seq');
> OJ> alter table xyz alter column foo set default '';
> OJ> COMMIT;
> OJ> Also, are you sure you want '' as a column default, and=20
> not ALTER COLUMN foo DROP DEFAULT?
> OJ> -Owen
>=20
> OK. THX. Second question:
>=20
> First, maybe set many fields with the same action - ex. set default?
>=20
> Ex. on mysql
>=20
> ALTER TABLE proc MODIFY name char(64) DEFAULT '' NOT NULL,
>                  MODIFY specific_name char(64) DEFAULT '' NOT NULL,
>                  MODIFY sql_data_access
>                         enum('CONTAINS_SQL',
>                              'NO_SQL',
>                              'READS_SQL_DATA',
>                              'MODIFIES_SQL_DATA'
>                             ) DEFAULT 'CONTAINS_SQL' NOT NULL....

Under PostgreSQL 7.4 you'd need to do those as three separate ALTER =
TABLE statements:

BEGIN;
ALTER TABLE proc ALTER name DEFAULT '' NOT NULL;
ALTER TABLE proc ALTER specific_name DEFAULT '' NOT NULL;
... and so on ...
COMMIT;

Note that ALTER TABLE under postgresql cannot change a column's type =
(including precision or length).  You can fake it by renaming the =
existing column, creating a new column of the appropriate type, =
UPDATEing data from the old column to the new column, [setting the new =
column's constraints,] and finally removing the old column, but it's a =
long-winded process.

> Second, can i modify more than 1 option with alter table on=20
> one field?:
>=20
> ex (mysql):
> ALTER TABLE proc MODIFY name varchar(64) DEFAULT '' NOT NULL;

Not under 7.4.