Stored functions and triggers - MySQL

A stored function in MySQL is a reusable program that is stored in the database and can be called multiple times. It performs a specific task and returns a single value as a result. Stored functions are commonly used for calculations, data manipulation, and complex data operations.

The keyword "FUNCTION" is used to create a stored function in MySQL. It is followed by the function name, input parameters, and the function body that contains the logic and calculations. A stored function is defined using the "CREATE FUNCTION" statement in MySQL.

A characteristic of stored functions in MySQL is that they can only return a single value. They are designed to perform a specific task and provide a result as a single value, such as a numeric value, string, or boolean.

The "CALL" statement is used to call a stored function in MySQL. It is followed by the function name and any required input parameters. The result of the function can be stored in a variable or used directly in a query.

The "DROP FUNCTION" statement is used to drop a stored function in MySQL. It removes the function definition and its associated code from the database. After dropping a function, it can no longer be invoked or used.

A trigger is a MySQL object that is used to automatically execute SQL statements in response to specific events, such as INSERT, UPDATE, or DELETE operations on a table. Triggers are defined to perform actions based on the occurrence of predefined events.

A characteristic of triggers in MySQL is that they are executed before a specific event occurs. Triggers are defined to perform actions before or after an event, such as before inserting a row into a table or after updating a record.

The keyword "BEFORE" is used to define the timing of a trigger in MySQL. It specifies that the trigger should be executed before the corresponding event, such as a row insertion, update, or deletion.

A stored function in MySQL would be useful in a scenario where you need to retrieve the total count of records in a table. The function can encapsulate the logic to calculate the count and return it as a single value.

A characteristic of triggers in MySQL is that they can modify data in the database. Triggers are capable of executing SQL statements that update, insert, or delete records based on specific events.

The "CREATE TRIGGER" statement is used to create a trigger in MySQL. It defines the trigger name, timing, event, and the actions to be performed when the event occurs.