1. Using SQL Query

To show all foreign keys in the PostgreSQL database, you can use the following SQL query:

SELECT conrelid::regclass AS table_name, 
       conname AS foreign_key, 
       pg_get_constraintdef(oid) 
FROM   pg_constraint 
WHERE  contype = 'f' 
AND    connamespace = 'public'::regnamespace   
ORDER  BY conrelid::regclass::text, contype DESC;

Sample result

The output of the SQL query:

In addition, to retrieve all foreign keys for a specific table in a PostgreSQL database you may use the following SQL query:

 SELECT conrelid::regclass AS table_name, conname AS foreign_key, pg_get_constraintdef(oid) FROM pg_constraint WHERE contype = 'f' and conrelid::regclass::text = 'your_table_name' AND connamespace = 'public'::regnamespace ORDER BY conrelid::regclass::text, contype DESC;