Re: alter table

Maciej Piekielniak wrote:
>
> Wednesday, February 15, 2006, 8:31:17 PM, you wrote:
> OJ> Note that prior to 8.0 PostgreSQL does not support
> multiple ALTER actions in a single query.  To get an
> equivalent effect, wrap separate ALTER TABLE queries in a transaction:
>
> 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
> not ALTER COLUMN foo DROP DEFAULT?
> OJ> -Owen
>
> OK. THX. Second question:
>
> First, maybe set many fields with the same action - ex. set default?
>
> Ex. on mysql
>
> 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
byrenaming the existing column, creating a new column of the appropriate type, UPDATEing data from the old column to
thenew 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
> one field?:
>
> ex (mysql):
> ALTER TABLE proc MODIFY name varchar(64) DEFAULT '' NOT NULL;

Not under 7.4.