Mysql procedure vs function, which would I use when?

sql

transaction-management

database-security

performance-optimization

byAnton Shumikhin·Jan 7, 2025

Go for a MySQL function when you want to return a value, wrapping your logic neatly in a SQL expression.

CREATE FUNCTION get_tax(rate DECIMAL, amount DECIMAL) RETURNS DECIMAL
   -- Because taxes, right? 😅
   RETURN rate * amount;

Bust it out with: SELECT get_tax(0.08, subtotal) FROM orders;

Spin up a MySQL procedure for more involved tasks which don't demand a return value, or need to dance a control flow waltz with loops and conditionals.

CREATE PROCEDURE process_order(order_id INT)
   -- Take the order, but hold the mustard 🚫🌭
   UPDATE orders SET status = IF(in_stock(order_id), 'Approved', 'Pending') WHERE id = order_id;

Get it rolling with: CALL process_order(123);

You use functions as part of SQL queries when you're handling scalar values, but you pull out procedures when you've got a more extensive, multi-stepped operation to perform.

Understanding the differences

Transaction control with procedures

When it's all about transaction management, procedures step up to the plate. They're happy to juggle multiple operations in a single transaction, tossing in COMMIT and ROLLBACK satements for good measure.

Lightweight functions

If it's a case of more straightforward computational tasks, opt for a function. Use them to embed logic directly into a query, perfect for a SELECT statement or WHERE clause.

Recursion and state changes in procedures

Procedures freely allow for recursion, also offering the ability to modify the database's state. In contrast, functions are predictably non-recursive, always preserving the database's state without alterations.

Functions in SQL expressions

Functions integrate beautifully into SQL queries, playing nicely with SELECT, WHERE, and other SQL commands. Procedures, however, demand an explicit CALL statement and freestand, separate from SQL queries.

Practical use cases and tips

Error handling in procedures

Procedures promote robust error handling, enabling you to craft responses to various unexpected conditions. They're ideal for implementing thorough error-catching mechanisms.

No side effects with functions

Functions are designed to be free from side effects. Anticipate the same output for any given input, promoting reproducibly consistent results.

Secure operations

Employ procedures and functions to encapsulate operations, limiting direct table access. This approach boosts your database security, presenting specific functionality while keeping underlying table details hidden.

Performance considerations

Despite the simplicity and reusability of functions, they could lead to performance hits if utilized excessively within a query. For frequently executed complex logic, consider using procedures and explore caching their results where appropriate.

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