Practical guide

SQL CREATE TABLE and Primary Keys: A Beginner's Guide

A table definition is a contract for the data it can store. Choose types and constraints that match the actual data and the database system in use.

What to do

  1. Sketch each field, its expected type, and whether a value is required before writing the CREATE TABLE statement.
  2. A simple pattern is CREATE TABLE departments (id INTEGER PRIMARY KEY, name VARCHAR(100) NOT NULL);.
  3. Use a primary key to identify each row uniquely. Add a foreign key when a relationship should reference another table.
  4. Test inserts with valid, duplicate, missing, and boundary values in a development database before relying on the schema.

Checks and limitations

  • Identity or auto-increment syntax differs among database engines; check the documentation for the specific system.
  • Do not make a field NOT NULL or UNIQUE without confirming the real data meets that rule.