PostgreSQL — Primary Key

Basic Primary Key

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100)
);

Named Primary Key

CREATE TABLE users (
    id SERIAL,
    name VARCHAR(100),
    CONSTRAINT pk_users PRIMARY KEY (id)
);

Composite Primary Key

CREATE TABLE enrollments (
    student_id INTEGER,
    course_id INTEGER,
    PRIMARY KEY (student_id, course_id)
);

Add Primary Key

ALTER TABLE users ADD PRIMARY KEY (id);
ALTER TABLE users ADD CONSTRAINT pk_users PRIMARY KEY (id);

Drop Primary Key

ALTER TABLE users DROP CONSTRAINT pk_users;

Auto Increment

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100)
);

UUID Primary Key

CREATE TABLE users (
    id UUID DEFAULT gen_random_uuid() PRIMARY KEY,
    name VARCHAR(100)
);

Mini Practice

1. Create primary key
2. Create composite key
3. Add primary key to existing table
4. Use UUID as primary key

Up Next

Continue with Foreign Key — foreign key constraints.