PostgreSQL · question
Q.05 of 36
What is a foreign key and how does it work in PostgreSQL?
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A foreign key establishes and enforces a link between data in two tables. It prevents actions that would destroy links between tables.
CREATE TABLE departments (
dept_id SERIAL PRIMARY KEY,
dept_name VARCHAR(100)
);
CREATE TABLE employees (
emp_id SERIAL PRIMARY KEY,
emp_name VARCHAR(100),
dept_id INTEGER REFERENCES departments(dept_id)
);
Foreign key constraints ensure referential integrity by preventing:
- Insertion of records with non-existent foreign key values
- Deletion of referenced records (unless CASCADE is specified)
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