In-depth understanding of the differences between Oracle stored procedures and functions

Oracle's stored procedures and functions are two commonly used storage objects in the database. They are a set of SQL statements that are pre-compiled and stored in the database, but there are some limitations in their use. difference. This article will delve into the differences between Oracle stored procedures and functions and provide specific code examples to demonstrate them.

1. The definition and difference between stored procedures and functions

1. ## Stored procedures：

   Stored procedures are a set of SQL statements that complete specific tasks, helping to improve code reusability and maintainability.
   • Stored procedures can contain input parameters, output parameters and return parameters, and can complete a series of operations and return results.
   • Stored procedures cannot be called individually and usually need to be executed through a calling statement.

2. Function:

   A function is a piece of SQL code that can return a value, usually used to calculate and return a single value .
   • Function can be called as part of an expression and directly returns the calculation result.
   • A function can have zero or more input parameters, but must return a value.

2. Specific examples of stored procedures and functions

1. Examples of stored procedures:

CREATE OR REPLACE PROCEDURE get_employee_info (employee_id IN NUMBER, emp_name OUT VARCHAR2)
IS
BEGIN
    SELECT last_name INTO emp_name
    FROM employees
    WHERE employee_id = employee_id;
END;
/

The above stored procedure is called get_employee_info, receives an employee ID as an input parameter, and returns the employee name as an output parameter.

Execute stored procedure:

DECLARE
    emp_name VARCHAR2(50);
BEGIN
    get_employee_info(100, emp_name);
    DBMS_OUTPUT.PUT_LINE('Employee name is: ' || emp_name);
END;
/

2. Function example:

CREATE OR REPLACE FUNCTION calculate_total_salary (employee_id IN NUMBER) RETURN NUMBER
IS
    total_salary NUMBER;
BEGIN
    SELECT sum(salary)
    INTO total_salary
    FROM salaries
    WHERE emp_id = employee_id;
    
    RETURN total_salary;
END;
/

The above function is named calculate_total_salary and receives an employee ID as Input parameters, calculate and return the employee's total salary.

Calling functions:

DECLARE
    emp_id NUMBER := 100;
    total_salary NUMBER;
BEGIN
    total_salary := calculate_total_salary(emp_id);
    DBMS_OUTPUT.PUT_LINE('Total salary for employee ' || emp_id || ' is: ' || total_salary);
END;
/

3. Applicable scenarios for stored procedures and functions

• Stored procedures are usually used It is suitable for performing a series of database operations and is suitable for handling complex business logic and data processing.
• Function is suitable for calculating and returning a single value, improving data reusability and code simplicity.

Conclusion:

Stored procedures and functions play an important role in Oracle database, but in actual applications, appropriate storage needs to be selected according to needs object. Stored procedures are suitable for handling complex business logic, while functions are better suited for calculating and returning a single value. Mastering the differences between stored procedures and functions will enable you to better perform database programming and optimization.

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