Functions vs Stored Procedures in MySQL: Differences

Stored functions and stored procedures both encapsulate logic in the database, but they serve different roles: functions compute and return one value inside queries, procedures perform actions when called.

Key Points

• Function must RETURN exactly one value; procedure returns none (uses OUT params)
• Functions are used inside SQL: SELECT tax(amount) FROM orders;
• Procedures run standalone: CALL monthly_cleanup();
• Procedures can run transactions and DML freely; functions are restricted
• Functions take only IN parameters; procedures take IN/OUT/INOUT
• Rule of thumb: calculations → function, processes → procedure