Functions¶

A function in MySQL is a reusable block of code that performs a specific task and returns a value. It allows users to encapsulate logic, modularize code, and perform complex calculations or data manipulations.

Advantages of Using Functions:¶

Benefits	Description
Reusability	Functions can be reused multiple times in different parts of a SQL statement or query, reducing code duplication and promoting code modularity and maintainability.
Encapsulation	Functions encapsulate logic and calculations, making it easier to understand and manage complex operations within the database.
Performance	Functions can improve query performance by reducing the amount of data transferred between the database server and the client application.
Customization	Functions allow users to create custom data transformations and calculations tailored to specific business requirements, enhancing the flexibility of the database.

Disadvantages of Using Functions:¶

Disadvantages	Description
Performance	Functions may introduce performance overhead, particularly if they involve complex computations or require access to large datasets.
Maintenance	Functions require maintenance to keep them synchronized with changes to the underlying data model or business logic. Changes may impact the behavior of dependent queries.
Portability	Functions written in MySQL may not be compatible with other database systems, limiting the portability of applications and databases.
Security	Improperly designed or implemented functions may pose security risks, such as SQL injection vulnerabilities or unauthorized access to sensitive data.

Create function¶

mysql> CREATE FUNCTION calculate_discount (total_amount DECIMAL(10, 2)) RETURNS DECIMAL(10, 2)
    -> BEGIN
    ->     DECLARE discount DECIMAL(10, 2);
    ->     IF total_amount > 100 THEN
    ->         SET discount = total_amount * 0.1;
    ->     ELSE
    ->         SET discount = 0;
    ->     END IF;
    ->     RETURN discount;
    -> END;

Call function¶

mysql> SELECT calculate_discount(120);

Drop function¶

mysql> DROP FUNCTION IF EXISTS calculate_discount;

Advanced SQL features¶

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Last update: 2024-05-03