I'm new to Postgres. I would like add a comment to my column mod in a table called app-user-bookings

I have tried this sql code:

alter table app_user_bookings
modify column mod 
int default 1 
comment "1# mobile booking,    2# admin booking,    3# web booking, 4# tell call";

But which didn't help me, can anyone help me?

  • 1
    For the record, here is the comment section of the documentation
    – Sahap Asci
    Commented Jan 11, 2017 at 6:03
  • 1
    You should also add a check constraint that makes sure the column does not store any other value then mentioned in the comment.
    – user1822
    Commented Mar 9, 2017 at 7:21
  • 1
    @a_horse_with_no_name I've incorporated your suggestion in the answer. Commented Mar 9, 2017 at 10:20

1 Answer 1


To update comment, don't use alter command.

Here is the PostgreSQL syntax:

comment on column app_user_bookings.mod is '1# mobile booking,    2# admin booking,    3# web booking, 4# tell call'

It makes sense to add a check to prevent wrong values appearing:

ALTER TABLE app_user_bookings
ADD CHECK (mod IN (1,2,3,4));

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