UNIQUE constraint

Force unique values with UNIQUE.

What is a constraint?

A constraint is a restriction applied to table data. It prevents bad input and keeps integrity.

CREATE TABLE products (
  id INT PRIMARY KEY,
  name VARCHAR(100) NOT NULL
);

PRIMARY KEY and NOT NULL are constraints.

The table products is created.

Constraints keep data consistent. They block bad inserts and updates. PRIMARY KEY, UNIQUE, NOT NULL, CHECK and FOREIGN KEY are common.

Create products with id INT PRIMARY KEY and name VARCHAR(100) NOT NULL.

Show example solution

CREATE TABLE products (
  id INT PRIMARY KEY,
  name VARCHAR(100) NOT NULL
)

Add constraint

CREATE TABLE products (
  id INT PRIMARY ____,
  name VARCHAR(100)
);

Show answer

CREATE TABLE products (
  id INT PRIMARY KEY,
  name VARCHAR(100)
);