What is the difference between a procedure and a function in PL/SQL?
Jun 21, 2025 am 12:05 AM
In PL/SQL, the core difference between a procedure and a function is its purpose and return value: 1. The procedure is used to perform operations, and does not force a return value, but can return multiple values ??through the OUT parameter; 2. The function is used to calculate and return a single value, which is often used in expressions or SQL statements; for example, the update_salary procedure can perform update operations, while the get_bonus function returns the calculated bonus amount; the procedure is suitable for data modification and multiple output scenarios, and the function is suitable for calculation logic that needs to be embedded in SQL; in addition, functions can be called in the process, but procedures cannot be called directly in the SQL statement.
In PL/SQL, the main difference between a procedure and a function comes down to their purpose and how they're used. Procedures are meant for performing actions, while functions are designed to compute and return a value.
What a Procedure Does
A procedure is like a small program that does something—like inserting data, updating records, or performing a series of SQL operations. It doesn't have to return anything, although it can use OUT parameters to send values ??back.
For example:
CREATE OR REPLACE PROCEDURE update_salary (emp_id IN NUMBER) IS BEGIN UPDATE employees SET salary = salary * 1.1 WHERE employee_id = emp_id; END;
You'd call this with:
EXEC update_salary(101);
- Procedures are good when you don't need a direct return value.
- They can modify data or perform logic without needing to give something back immediately.
- You can use them in anonymous blocks or call them from other procedures.
How a Function Is Different
A function, on the other hand, must return a value. That makes it useful in expressions or SQL statements where a value is expected.
Here's a basic function:
CREATE OR REPLACE FUNCTION get_bonus (emp_id IN NUMBER) RETURN NUMBER IS bonus_amt NUMBER; BEGIN SELECT salary * 0.1 INTO bonus_amt FROM employees WHERE employee_id = emp_id; RETURN bonus_amt; END;
And you'd use it like this:
SELECT get_bonus(101) FROM dual;
- Functions are ideal when you need to calculate and return a result.
- They're often used inside SQL queries or assignments.
- Be careful: if your function has DML (like INSERT or UPDATE), you might run into issues using it directly in SQL unless you define it with
PRAGMA AUTONOMOUS_TRANSACTIONor allow side effects.
When to Use Which
Use a procedure when:
- You're doing an action rather than calculating a value.
- You want to change data (like inserts, updates, deletes).
- You need multiple outputs via OUT parameters.
Use a function when:
- You need to return a single value for use elsewhere.
- You plan to call it inside a SQL query or expression.
- The logic is more about transformation or calculation than modification.
Also keep in mind:
- Functions can be called from within procedures.
- Procedures can't be directly called from a SQL statement unless wrapped in a function or used via a ref cursor.
So, basically:
- Procedures do things , optionally returning values ??through OUT parameters.
- Functions return a value , and are usually used where a computed result is needed.
That's the core distinction — not too complicated once you see how each fits into real usage.
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