Postgres: remove check constraint on varchar column

Question

I'm coming from a MySQL world and am having a hard time doing things in PostgreSQL.

I have a column which looks like this in my GUI client:

I'm not sure if it is an enum column, or a varchar with a constraint (are they the same thing in postgres?)

I want to change the type of the column to a varchar/string. I've tried this:

ALTER TABLE tablename ALTER COLUMN type TYPE character varying(255);

but no luck, I still see the constraints on the column

it looks like it is already a character varying column and the thing that you are talking about is indeed a constraint, if you want to get rid of it you should take a look at DROP CONSTRAINT statement — mic4ael
– mic4ael, Commented Sep 1, 2016 at 19:46
@a_horse_with_no_name The tables were created with an ORM and my GUI does not give me a "copy as SQL" type function where I would be able to show how this column can be replicated. — Zaki Aziz
– Zaki Aziz, Commented Sep 1, 2016 at 20:19

Zaki Aziz · Accepted Answer · 2016-09-01 19:57:22Z

24

I was able to solve this issue with some guidance from @mich4ael's helpful comment

ALTER TABLE tablename DROP CONSTRAINT constraint_name;

answered Sep 1, 2016 at 19:57

Zaki Aziz

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3 Comments

DavidsKanal Over a year ago

Could you please specify what coinstraint_name refers to? Is it type? type::text? What is it, where do I find it?

Zaki Aziz Over a year ago

@DavidsKanal It's been many years since I wrote this answer so i'm missing a lot of context, but if you want to know what constraints are I'd suggest reading over this on the postgres docs: postgresql.org/docs/15/ddl-constraints.html

DavidsKanal Over a year ago

Ah, it's alright, I managed to find the answer. Turns out that every constraint has a name, even if you didn't specify one. I needed to manually query one of the meta tables in the database to get a list of constraints and their names, and that way, I was able to find the constraint's name.

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