Boolean operators (AND, OR, NOT) combine multiple conditions into complex filters. Parentheses control evaluation order for precise logic.

**Boolean Operators:**

AND: Both conditions must be true

WHERE age > 18 AND status = 'active'

OR: At least one condition must be true

WHERE status = 'pending' OR status = 'processing'

NOT: Negates condition

WHERE NOT status = 'cancelled'

**Precedence (without parentheses):**

1. NOT (highest)

2. AND

3. OR (lowest)

**Parentheses Override Precedence:**

WHERE (status = 'active' OR status = 'pending') AND age > 18

**Evaluation Order:**

Database evaluates left to right within same precedence level.

**Best Practice:**

Always use parentheses for clarity, even when not strictly needed.

Essential for all SQL developers building search features, business rules, and data validation logic.

Complex filters power advanced searches: find high-value active customers in specific regions, filter products by multiple criteria, build sophisticated business rules.