SQL Stored Procedures

In SQL, a stored procedure is a precompiled and stored set of SQL statements that can be executed on demand. Stored procedures are often used for complex database operations that require multiple steps, such as inserting or updating multiple rows, or performing complex calculations or data manipulations.

Stored procedures can be created and stored in the database using the CREATE PROCEDURE statement. The procedure definition includes the SQL code that will be executed when the procedure is called, as well as any input or output parameters that are required. For example:

CREATE PROCEDURE update_employee_salary (
  IN employee_id INT,
  IN salary DECIMAL(10,2)
)
BEGIN
  UPDATE employees SET salary = salary WHERE id = employee_id;
END

This creates a stored procedure called update_employee_salary that takes two input parameters: employee_id, which is an integer that identifies the employee whose salary should be updated, and salary, which is a decimal value that specifies the new salary. The procedure simply updates the salary column of the employees table for the specified employee.

Once a stored procedure has been created, it can be executed using the CALL statement, followed by the name of the procedure and any input parameters that are required. For example:

CALL update_employee_salary(12345, 75000.00);

This calls the update_employee_salary procedure and passes in the values 12345 and 75000.00 for the employee_id and salary parameters, respectively.

Stored procedures can be useful for a variety of purposes, such as:

• Reducing network traffic by executing multiple SQL statements in a single call
• Encapsulating complex business logic in the database for better security and maintainability
• Improving performance by precompiling SQL statements and reducing parsing and optimization overhead
• Allowing multiple users or applications to execute the same SQL code without duplicating the code in each application.