Add primary key to PostgreSQL table only if it does not exist
Why not include the PK definition inside the CREATE TABLE:
CREATE TABLE IF NOT EXISTS mail_app_recipients( id_draft Integer NOT NULL, id_person Integer NOT NULL, constraint pk_mail_app_recipients primary key (id_draft, id_person))
You could do something like the following, however it is better to include it in the create table as a_horse_with_no_name suggests.
if NOT exists (select constraint_name from information_schema.table_constraints where table_name = 'table_name' and constraint_type = 'PRIMARY KEY') thenALTER TABLE table_name ADD PRIMARY KEY (id);end if;
You can try to DROP it before creating it (DROP has the IF EXISTS clause):
ALTER TABLE mail_app_recipients DROP CONSTRAINT IF EXISTS mail_app_recipients_pkey;ALTER TABLE mail_app_recipients ADD CONSTRAINT mail_app_recipients_pkey PRIMARY KEY ("id_draft","id_person");Note that this require that you give a name to the primary key constraint - in this example mail_app_recipients_pkey.