set default value to null on postgresql

Question

I read here that I should be able to set the default value of a column like this:

ALTER [ COLUMN ] column SET DEFAULT expression

But this:

ALTER address.IsActive SET DEFAULT NULL

Gives me this error:

ERROR: syntax error at or near "address" LINE 1: ALTER address.IsActive SET DEFAULT NULL

What have I done wrong? Also, how can I specify multiple columns to have their default value be NULL?

Answer 1

The correct syntax is:

ALTER TABLE table_name ALTER COLUMN column_name SET DEFAULT NULL;

For several columns you repeat the ALTER COLUMN part as documented in the manual:

ALTER TABLE table_name 
    ALTER COLUMN foo SET DEFAULT NULL,
    ALTER COLUMN bar SET DEFAULT 0;

Answer 2

alter table dogs
alter column breed set default 'boxer'

alter table dogs
alter column breed set default null