Identity Column

An identity column automatically generates a unique, usually sequential, integer value for every new row — the standard SQL way (GENERATED ... AS IDENTITY) to create an auto-incrementing surrogate key without managing a sequence yourself.

Under the hood, most databases implement identity columns using a sequence generator, but the identity syntax ties that sequence directly to the column and handles the bookkeeping automatically. It replaces older, vendor-specific mechanisms — MySQL's AUTO_INCREMENT, SQL Server's IDENTITY property, and Oracle's older "sequence + trigger" pattern (Oracle 12c+ supports the standard identity syntax directly).

CREATE TABLE employees (
  employee_id NUMBER GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  first_name  VARCHAR2(50)
);