Logical Operators

Logical operators combine boolean expressions and return a boolean result. They are commonly used in WHERE clauses to combine multiple conditions.

Syntax

-- AND/OR
boolean_expression operator boolean_expression

-- NOT
NOT boolean_expression

Operators

Operator	Description
`AND`	Returns true if both expressions are true
`OR`	Returns true if either expression is true
`NOT`	Returns the opposite of the expression's value

Examples

AND

-- Select customers who are both from California AND have made a purchase
SELECT * FROM customers
WHERE state = 'CA' AND purchases > 0;

OR

-- Select products that are either electronics OR cost more than $100
SELECT * FROM products
WHERE category = 'Electronics' OR price > 100;

NOT

-- Select cities that are not in Texas
SELECT * FROM cities
WHERE NOT (state_code = 'TX');

-- Alternative form using inequality
SELECT * FROM cities
WHERE state_code <> 'TX';

Combining Multiple Operators

-- Select products that are in stock and either on sale or under $20
SELECT * FROM products
WHERE in_stock = true
  AND (on_sale = true OR price < 20);

Note: When combining operators, parentheses can be used to control the order of evaluation.