I'm new to PostgreSQL and that is why I'm asking this question. I have a table app_client_users and a column named client_id. Initially I set it as NOT NULL and now I would like to change it to allow NULL. I've tried

alter table app_client_users alter column client_id int  NULL ;


alter table app_client_users alter column client_id   NULL ;

which is not working. How can I fix it?

  • 1
    Please be aware that psql is a client to PostgreSQL, not a nickname of the latter. Commented Jan 3, 2017 at 11:30

1 Answer 1


You can simply drop NOT NULL

ALTER TABLE app_client_users ALTER COLUMN client_id DROP NOT NULL;

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