How to list PostgreSQL table constraints

Question: How can I list the Constraints on a PostgreSQL table ? 

Answer: This script will list PostgreSQL constraints . It achieves the results  via the pg_catalog.pg_constraint   - which checks primary key, unique, foreign key, and exclusion constraints on tables.

SELECT con.* FROM pg_catalog.pg_constraint con

INNER JOIN pg_catalog.pg_class rel ON rel.oid = con.conrelid

INNER JOIN pg_catalog.pg_namespace nsp ON nsp.oid = connamespace

WHERE nsp.nspname = 'my_schema_name'

AND rel.relname = 'my_table_name';

PostgreSQL cheatsheet