A stored procedure is a set of SQL statements that are precompiled and stored in a database. It can be executed repeatedly with different parameters and can be used to perform complex data operations.

Stored procedures are often used in database management systems to encapsulate business logic or complex processing tasks. A stored procedure can be called by another SQL statement or program, making it a reusable and efficient way to execute complex database operations.

Example

Let's say you have a database that stores information about customers and their orders. You want to create a stored procedure to retrieve all orders for a specific customer.

CREATE PROCEDURE GetOrdersForCustomer 
@CustomerID int 
AS 
BEGIN 
SELECT * 
FROM Orders 
WHERE CustomerID = @CustomerID 
END

This stored procedure takes a single parameter, which is the customer ID, and returns all orders for that customer.

To execute the stored procedure, you would simply call it with the appropriate parameter:

EXEC GetOrdersForCustomer @CustomerID = 1234

This would retrieve all orders for the customer with ID 1234.

Stored procedures can also be used to perform other operations, such as inserting, updating, and deleting data. Here's an example of a stored procedure that inserts a new customer into the database:

CREATE PROCEDURE InsertCustomer 
@Name varchar(50), 
@Address varchar(100), 
@City varchar(50), 
@State varchar(50), 
@Zip varchar(10) 
AS 
BEGIN 
INSERT INTO Customers (Name, Address, City, State, Zip) 
VALUES (@Name, @Address, @City, @State, @Zip) 
END

This stored procedure takes five parameters, which are the customer's name, address, city, state, and zip code. It inserts a new record into the Customers table with the specified values.

To execute the stored procedure, you would call it with the appropriate parameters:

EXEC InsertCustomer @Name = 'John Smith', @Address = '123 Main St', @City = 'Anytown', @State = 'CA', @Zip = '12345'

This would insert a new customer record with the specified values.

Basic Use Cases

1. Reusability: If you have a complex SQL statement that is used in multiple places, encapsulating it in a stored procedure can make it easier to maintain and reuse.

2. Security: Stored procedures can be used to restrict access to certain database operations or data, providing an additional layer of security.

3. Performance: Stored procedures are precompiled and stored in the database, making them faster to execute than ad-hoc SQL statements.

4. Abstraction: Stored procedures can be used to encapsulate business logic or complex processing tasks, making them easier to understand and maintain.

In summary, stored procedures are useful for performing complex data operations and improving performance and security. They can be used for a variety of tasks, such as retrieving data, inserting new records, updating existing records, and deleting data. Stored procedures can be called repeatedly with different parameters, making them a powerful tool for managing data in a database.