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SQL Constraints

Introduction
Primary keys
Foreign keys
9. Deleting foreign keys
Updating and deleting with foreign keys
Summary

Instruction

Nicely done! Now, we have the following table:

CREATE TABLE soccer_player (
  id integer PRIMARY KEY,
  first_name varchar(32),
  last_name varchar(32),
  team_id integer,
  FOREIGN KEY (team_id) REFERENCES soccer_team (id)
);

We want to get rid of the foreign key. We can use the following syntax:

ALTER TABLE soccer_player
DROP CONSTRAINT soccer_player_team_id_fkey;

The syntax for dropping foreign and primary keys is identical. The only thing you should keep in mind is PostgreSQL's default naming convention. For foreign keys, it's: the table_name + _ + column_name + _fkey. That's why the column named team_id in the soccer_player table (which is a foreign key) has a constraint named soccer_player_team_id_fkey.

Exercise

The table employee is currently created like this:

CREATE TABLE employee (
  id integer PRIMARY KEY,
  first_name varchar(32),
  last_name varchar(32),
  department_id integer,
  position_id varchar,
  FOREIGN KEY (department_id) REFERENCES department (id)
);

However, our company decided to create a new business model in which there are no fixed departments – each employee can work for multiple divisions. Your task is to get rid of the foreign key department_id.