Hi,
Please find a question that didn't get an answer in the pgsql-sql list. I hope I'll get an answer here. Thanks, Olivier De : Olivier Leprêtre [mailto:o.lepre...@gmail.com] Envoyé : mercredi 29 août 2018 15:49 À : 'pgsql-...@lists.postgresql.org' Objet : redundant constraint_schema Hi, Can someone explain why, when a column is not created (add column if not exists), a redundant constraint is still created from the REFERENCES part ? I have a patching script that is supposed to add column if not existing : ALTER TABLE myschem.table1 ADD COLUMN IF NOT EXISTS col1 VARCHAR(254) REFERENCES myschem.table2(col2) When col1 already exists, I expected that nothing would happen. But, when applying the previous query and then querying : select constraint_name from information_schema.key_column_usage where constraint_schema='myschem' I notice that a new constraint "table1_col2_fkeyxxx" is created each time the previous ALTER TABLE is called (with xxx being a new number each time) Thanks, Olivier
