How to setup a column constraint for an integer type? Default 0 if not defined

Wang, Mary Y wrote:

Hi,

I'm trying to port some source code to Postgres 8.3.8 and have been encountering some surprises :-(
I would like to set up a column constraint for an integer type, so that when the value is undefined, it would assign a default value of 0 to that column.
How would I do that in 8.3.8? Please provide an example.

when you say, 'value is undefined' do you mean, if an insert is done
without specifying that field ?

in that case, ou wouldn't use a constraint, you'd use a DEFAULT value,
like...

CREATE TABLE tblname (
....
somefield INTEGER DEFAULT 0,
....
);

or, if the table already exists...

ALTER TABLE tblname ALTER COLUMN somefield SET DEFAULT 0;