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ENUM types

Learning Focus

Use this lesson to model finite status values using PostgreSQL ENUM and understand maintenance tradeoffs.

Concept Overview​

Enums restrict a column to a set of named values.

CREATE TYPE order_status AS ENUM ('pending', 'paid', 'cancelled');

Example​

CREATE TABLE orders (
  order_id bigint GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  status order_status NOT NULL DEFAULT 'pending'
);

Add a new value:

ALTER TYPE order_status ADD VALUE 'refunded';

When to Use vs Avoid​

Use enums when:

  • the set is small and changes rarely

Avoid enums when:

  • the set changes frequently (consider a lookup table + FK)

What's Next​