SQL Stored Procedures

What is a Stored Procedure?

A stored procedure is a prewritten block of SQL code that can be stored in a database for reuse.

By saving frequently used SQL queries as stored procedures, you can easily execute them whenever needed.

Additionally, stored procedures can accept parameters, allowing them to adapt their actions based on the values passed to them.

Stored Procedure Syntax

CREATE PROCEDURE procedure_name
AS
sql_statement
GO;

Execute a Stored Procedure

EXEC procedure_name;

Demo Database

Here’s an excerpt from the “Customers” table in the Northwind sample database:

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

Stored Procedure Example

This SQL statement creates a stored procedure named “SelectAllCustomers” which retrieves all records from the “Customers” table:

Example

CREATE PROCEDURE SelectAllCustomers
AS
SELECT * FROM Customers
GO;

Execute the previously mentioned stored procedure in the following manner:

Example

EXEC SelectAllCustomers;

Stored Procedure With One Parameter

This SQL statement creates a stored procedure that retrieves customers from a specific city from the “Customers” table:

Example

CREATE PROCEDURE SelectAllCustomers @City nvarchar(30)
AS
SELECT * FROM Customers WHERE City = @City
GO;

Execute the aforementioned stored procedure as demonstrated below:

Example

EXEC SelectAllCustomers @City = ‘London’;

Stored Procedure With Multiple Parameters

Creating a stored procedure with multiple parameters is straightforward. Simply list each parameter along with its data type, separated by commas, as illustrated below:

The subsequent SQL statement generates a stored procedure that retrieves customers from a specific city and postal code from the “Customers” table:

Example

CREATE PROCEDURE SelectAllCustomers @City nvarchar(30), @PostalCode nvarchar(10)
AS
SELECT * FROM Customers WHERE City = @City AND PostalCode = @PostalCode
GO;

Execute the aforementioned stored procedure as follows:

Example

EXEC SelectAllCustomers @City = ‘London’, @PostalCode = ‘WA1 1DP’;