Sql Constraints

SQL constraints are rules that help keep data accurate and consistent.

• NOT NULL: Prevents a column from having empty values.
• UNIQUE: Makes sure all values in a column are different.
• CHECK: Adds a condition that the values in a column must meet.

Use case: If you're storing product prices, you can use a CHECK constraint to prevent negative values as shown in the snippet below:

CREATE TABLE products (
  id INT PRIMARY KEY,
  name VARCHAR(50) NOT NULL,
  price DECIMAL(10, 2) CHECK (price >= 0)
);