Stored Procedures and Functions

1. What are Stored Procedures?

A stored procedure is a precompiled collection of one or more SQL statements that can be executed as a single unit. They are stored in the database and can accept parameters.

Stored procedures are often used for tasks that involve multiple steps or complex logic.

2. Syntax of a Stored Procedure

The basic syntax for creating a stored procedure is as follows:

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CREATE PROCEDURE procedure_name (parameter_list)
BEGIN
    -- SQL statements
END;

3. Example of a Stored Procedure

Here’s an example of a stored procedure that retrieves a customer's details based on their ID:

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CREATE PROCEDURE GetCustomerDetails (IN customerID INT)
BEGIN
    SELECT * FROM Customers WHERE CustomerID = customerID;
END;

To call this procedure:

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CALL GetCustomerDetails(1);

4. What are Functions?

A function is a subroutine that can take parameters, perform a calculation or operation, and return a single value. Functions are commonly used to encapsulate reusable logic.

5. Syntax of a Function

The basic syntax for creating a function is as follows:

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CREATE FUNCTION function_name (parameter_list)
RETURNS return_data_type
BEGIN
    -- SQL statements
    RETURN value;
END;

6. Example of a Function

Here’s an example of a function that calculates the total price of an order including tax:

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CREATE FUNCTION CalculateTotalPrice (IN price DECIMAL(10,2), IN tax_rate DECIMAL(5,2))
RETURNS DECIMAL(10,2)
BEGIN
    RETURN price + (price * tax_rate);
END;

To call this function:

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SELECT CalculateTotalPrice(100.00, 0.07);

7. Differences Between Stored Procedures and Functions

8. Benefits of Using Stored Procedures and Functions

• Code Reusability: Both stored procedures and functions allow you to encapsulate logic for reuse, reducing code duplication.
• Improved Performance: Precompiled execution can lead to better performance compared to executing raw SQL statements.
• Enhanced Security: Access to underlying tables can be restricted while allowing execution of procedures and functions.
• Better Maintenance: Changes in logic can be made in one place, minimizing the impact on applications that use them.

9. Conclusion

Stored procedures and functions are powerful tools for managing complex database operations. Understanding when to use each can significantly enhance the efficiency and maintainability of your SQL database.