CREATE TABLE employee(emp_id SERIAL PRIMARY KEY, name VARCHAR(30), sector_fk INT NOT NULL); CREATE TABLE process(emp_id SERIAL PRIMARY KEY, sector VARCHAR(20)); ALTER TABLE employee ADD FOREIGN KEY (sector_fk) REFERENCES company(emp_id) ON DELETE CASCADE; -- Deletes cascade employees referencing deleted companies DELETE FROM company WHERE sector='industry';
Here is what the above code is Doing:
1. Create a table called company with a primary key called emp_id.
2. Create a table called employee with a primary key called emp_id.
3. Create a table called process with a primary key called emp_id.
4. Add a foreign key to the employee table that references the company table.
5. Delete all rows from the company table where the sector is industry.