SQL Relationships

Foreign Keys

ON DELETE CASCADE

sql - PostgreSQL: FOREIGN KEY/ON DELETE CASCADE - Stack Overflow

Deleting any clan (the other table) will delete any hobbits

If you delete a hobbit (current table), nothing will happen to the other table

• unless there's a many-to-many relationship

CREATE TABLE clan (
    id serial PRIMARY KEY,
    clan varchar
);

CREATE TABLE hobbit (
    id serial PRIMARY KEY,
    hobbit varchar,
    clan_id integer REFERENCES shire.clans (id) ON DELETE CASCADE
);

Are two tables the same?

SELECT CASE WHEN EXISTS (TABLE a EXCEPT TABLE b)
              OR EXISTS (TABLE b EXCEPT TABLE a)
            THEN 'different'
            ELSE 'same'
       END AS result ;

---

Last update: 2023-04-24