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Getting started with SQL Server stored procedures

By: Greg Robidoux | Read Comments (6) | Print

Greg is the President of Edgewood Solutions and a co-founder of MSSQLTips.com.

Related Tips: More

Problem
I have been using SQL Server for some time, but all of the code that is issued against the database is embedded in the application code. I know that you can create stored procedures, but I am not exactly sure where to start or what I need to do to implement stored procedures.

Solution
Stored procedures are nothing more that a batch of T-SQL statements that are stored in the database. Instead of having to issues multiple statements from your application you can issue one command to call the stored procedure to do a batch of work instead of just one statement. In addition, since the code is stored in the database you can issue the same set of code over and over again even from different applications or a query window. To get started the rest of this tip looks at some sample stored procedures and how you can get started and build upon them.

The below examples show you how simple it is to create stored procedures. All of these examples use the AdventureWorks database, but these should be pretty straightforward that you can apply these concepts to your own databases and applications.

Example 1 - simple stored procedure

This first example creates a simple stored procedure that gets the TOP 1 record from the Person.Contact table.

CREATE PROCEDURE uspGetContact 
AS 
SELECT TOP 1 ContactID, FirstName, LastName 
FROM Person.Contact

After the above has been created use the command below to execute this stored procedure.

EXEC uspGetContact

This is the results from this first query.

Example 2 - stored procedure with a parameter

This next example is a modification of the first example, but this time adding a parameter that is passed into the procedure to dynamically select the records. Instead of using CREATE PROCEDURE we are using ALTER PROCEDURE to modify the procedure that we created in Example 1 instead of dropping it first and then recreating it.

ALTER PROCEDURE uspGetContact @LastName NVARCHAR(50) 
AS 
SELECT TOP 1 ContactID, FirstName, LastName 
FROM Person.Contact 
WHERE LastName = @LastName

Below shows two different ways the stored procedure can be run. The first example just passes the parameter value we want to use and the second example also includes the parameter name along with the value. You can run the stored procedure with either one of these commands.

EXEC uspGetContact 'Alberts'

EXEC uspGetContact @LastName='Alberts'

This is the results from this first query.

Example 3 - stored procedure with a parameter and output parameter

In this example we have both an input parameter as well as an OUTPUT parameter. The output parameter will be used to pass back the ContactID that we are looking up in the stored procedure. This output parameter will then be used to select the persons ContactID, FirstName and LastName along with any address records for this person.

Again we are altering the stored procedure uspGetContact and then secondly we are running the next set of code that executes procedure uspGetContact and then based on the return value it gets it will also query for the persons name and address info.

ALTER PROCEDURE uspGetContact @LastName NVARCHAR(50), @ContactID INT output 
AS 
SELECT TOP 1 @ContactID = c.ContactID 
   FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
WHERE c.LastName = @LastName

After the stored procedure has been altered run the below block of code. This will execute the above stored procedure and if the ContactID has a value it will also return the person and address info.

DECLARE @ContactID INT 
SET @ContactID = 0 
EXEC uspGetContact @LastName='Smith', @ContactID=@ContactID OUTPUT 
IF @ContactID <> 0 
BEGIN 
   SELECT ContactID, FirstName, LastName 
   FROM Person.Contact 
   WHERE ContactID = @ContactID 

   SELECT d.AddressLine1, d.City, d.PostalCode 
   FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
   WHERE c.ContactID = @ContactID 
END

This is the results from this first query.

Example 4 - stored procedure using the RAISERROR statement

In this example we are combining the two steps in Example 3 into one stored procedure. The first step is to get the ContactID and then the second part of the procedure will lookup the persons name and address info. We also added in code to use the RAISERROR statement to return an error if no records are found.

This is then being run twice to show what it looks like when data is found and when no data is found. The RAISERROR statement can be used to control how your application handles no data or any other error that may occur.

ALTER PROCEDURE uspGetContact @LastName NVARCHAR(50) 
AS 
DECLARE @ContactID INT 
SELECT TOP 1 @ContactID = c.ContactID 
FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
WHERE c.LastName = @LastName 

IF @@ROWCOUNT > 0 
BEGIN 
   SELECT ContactID, FirstName, LastName 
   FROM Person.Contact 
   WHERE ContactID = @ContactID 
    
   SELECT d.AddressLine1, d.City, d.PostalCode 
   FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
   WHERE c.ContactID = @ContactID 
END 
ELSE 
BEGIN 
   RAISERROR ('No record found',10,1) 
END

EXEC uspGetContact @LastName='Walters'

This is the results from this first query.

EXEC uspGetContact @LastName='Job'

This is the results from this first query when no data is found.

Example 5 - stored procedure with a separate calling stored procedure

Here is another example where we have two stored procedures. The first stored procedure uspFindContact lookups the first record that has an address record and then returns the ContactID to the calling stored procedure to again display the person and address info.

CREATE PROCEDURE uspFindContact @LastName NVARCHAR(50), @ContactID INT output 
AS 
SELECT TOP 1 @ContactID = c.ContactID 
   FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
WHERE c.LastName = @LastName

The code below does an alter of the uspGetContact stored procedure that calls uspFindContact and returns the recordsets.

ALTER PROCEDURE uspGetContact @LastName NVARCHAR(50) 
AS 
DECLARE @ContactID INT 
SET @ContactID = 0 

EXEC uspFindContact @LastName=@LastName, @ContactID=@ContactID OUTPUT 

IF @ContactID <> 0 
BEGIN 
   SELECT ContactID, FirstName, LastName 
   FROM Person.Contact 
   WHERE ContactID = @ContactID 

   SELECT d.AddressLine1, d.City, d.PostalCode 
   FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
   WHERE c.ContactID = @ContactID 
END 
ELSE 
BEGIN 
   RAISERROR ('No record found',10,1) 
END

EXEC uspGetContact @LastName='Walters'

This is the results from this first query.

EXEC uspGetContact @LastName='Job'

This is the results from this first query.

Example 6 - stored procedure with comments

This last example takes the uspGetContact stored procedure and adds comments to the code so you can see how comments work within a stored procedure. You can see that there are two ways that comments can be made. 1) using -- and 2) using /* to begin the comment block and */ to end the comment block. Other than that nothing else has changed.

ALTER PROCEDURE uspGetContact @LastName NVARCHAR(50) 
AS 
/* This is a sample stored procedure to show 
   how comments work within a stored procedure */ 

-- declare variable 
DECLARE @ContactID INT 
-- set variable value 
SET @ContactID = 0 

-- execute stored proc and return ContactID value 
EXEC uspFindContact @LastName=@LastName, @ContactID=@ContactID OUTPUT 

-- if ContactID does not equal 0 then return data else return error 
IF @ContactID <> 0 
BEGIN 
   SELECT ContactID, FirstName, LastName 
   FROM Person.Contact 
   WHERE ContactID = @ContactID 

   SELECT d.AddressLine1, d.City, d.PostalCode 
   FROM HumanResources.Employee a  
       INNER JOIN HumanResources.EmployeeAddress b ON a.EmployeeID = b.EmployeeID 
       INNER JOIN Person.Contact c ON a.ContactID = c.ContactID 
       INNER JOIN Person.Address d ON b.AddressID = d.AddressID 
   WHERE c.ContactID = @ContactID 
END 
ELSE 
BEGIN 
   RAISERROR ('No record found',10,1) 
END

These are pretty simple examples, but hopefully this gives you an idea of how easy it is to create stored procedures for SQL Server. If you can run a SELECT statement from either a query window or from your application you can just as easily run a stored procedure as show above.

Next Steps

If you are not already using stored procedures hopefully this gives you some insight as to what you need to do to begin using them
As mentioned these are pretty simple examples, but just about anything you can do with a batch of statements can be combined into a stored procedure and then used over and over again for your applications.

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Last Update: 5/9/2008

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Comments and Feedback:

Thursday, September 18, 2008 - 12:08:47 AM - mateia Read The Tip

Hello,

Related to this code:

CREATE PROCEDURE uspGetContact 
AS 
SELECT ContactID, FirstName, LastName 
FROM Person.Contact

EXEC uspGetContact

After calling EXEC uspGetContact, I would like in Transact-SQL to get the actual rows (dataset) selected by the uspGetContact stored procedure. Is it possible to have something like this:

EXEC uspGetContact

SELECT * FROM DataSetReturnedByuspGetContact ??

If it's not possible to do this in Transact-SQL, then how can application programs written in any language: e.g. C++, Delphi, Visual Basic receive a recordset/dataset without any modification of the 'uspGetContact' stored procedure ??

Thank you very much

Thursday, September 18, 2008 - 6:42:07 AM - aprato

Read The Tip

There are a few ways. Below is one approach.

CREATE PROCEDURE dbo.uspGetContact
AS
SET NOCOUNT ON

SELECT ContactID, FirstName, LastName
FROM Person.Contact

return @@rowcount
go

declare @rows int
exec @rows = dbo.uspGetContact
select @rows

Thursday, September 18, 2008 - 6:51:39 AM - mateia

Read The Tip

Hello,

Thank you for your reply.

However, maybe I wasn't clear enough, after calling the stored procedure I need the actual selected rows, not the number of selected rows.

I'm afraid is not possible without an OUTPUT parameter returning the selected rows in a cursor.

Thursday, September 18, 2008 - 6:57:47 AM - aprato

Read The Tip

Your language of choice does not have a ResultSet type object?

In T-SQL, you can create a temp table/table variable to capture outputted rows.

Thursday, September 18, 2008 - 7:11:48 AM - mateia

Read The Tip

Hello

>In T-SQL, you can create a temp table/table variable to capture outputted rows.

Please see the example below:

USE [Northwind]
GO

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE SelectCustomers
AS
BEGIN
SELECT * FROM Customers
END
GO

EXEC [SelectCustomers]

How can I access here in Transact-SQL, the rows returned by the SelectCustomers stored procedure ?

Thursday, September 18, 2008 - 7:54:30 AM - aprato

Read The Tip

You create a temp table

CREATE PROCEDURE SelectCustomers
AS
BEGIN
SELECT * FROM Customers
END
GO

create table mytable(column_list....)

insert into mytable(column_list....)
EXEC [SelectCustomers]

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