FOREIGN KEY

Relate two tables with FOREIGN KEY.

CHECK

With CHECK you apply a condition to a column. Values failing the condition cannot be inserted.

CREATE TABLE products (
  id INT PRIMARY KEY,
  price DECIMAL(10,2) CHECK (price > 0)
);

Price must be positive; negative prices are blocked.

The table products is created.

The CHECK condition is verified on every INSERT and UPDATE. Complex conditions work too: CHECK (price > 0 AND stock >= 0).

Create products with id INT PRIMARY KEY and price DECIMAL(10,2) CHECK (price > 0).

Show example solution

CREATE TABLE products (
  id INT PRIMARY KEY,
  price DECIMAL(10,2) CHECK (price > 0)
)

Apply check

CREATE TABLE products (
  price DECIMAL(10,2) ____ (price > 0)
);

Show answer

CREATE TABLE products (
  price DECIMAL(10,2) CHECK (price > 0)
);

Next lesson: CASCADE