Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 12: Stored Procedures
Supplying Default Values
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To make a parameter optional, you have to supply a default value. To do this, you just add an = together
with the value you want to use for a default after the data type, but before the comma. Once you’ve done
this, the users of your sproc can decide to supply no value for that parameter, or they can provide their
own value.
So, for example, if we wanted to allow the parameter in our previous example to be optional, we would
just modify the parameter declaration to include a default:
USE AdventureWorks2008;
DROP PROC spEmployeeByName; -- Get rid of the previous version
GO
CREATE PROC spEmployeeByName
@LastName nvarchar(50) = NULL
AS
IF @LastName IS NOT NULL
SELECT p.LastName, p.FirstName, e.JobTitle, e.HireDate
FROM Person.Person p
JOIN HumanResources.Employee e
ON p.BusinessEntityID = e.BusinessEntityID
WHERE p.LastName LIKE @LastName + ‘%’;
ELSE
SELECT p.LastName, p.FirstName, e.JobTitle, e.HireDate
FROM Person.Person p
JOIN HumanResources.Employee e
ON p.BusinessEntityID = e.BusinessEntityID;
Notice how I have made use of the control of flow constructs we learned in the previous chapter on
scripting to decide which is the better query to run. The differences are subtle, with only the addition of
a WHERE clause really differentiating the choices.
Given our new default, we can now run the sproc without a parameter:
EXEC spEmployeeByName;
And, as expected, we get a more full result set:
LastName FirstName JobTitle HireDate
------------ ------------ ----------------------------- ----------
Sánchez Ken Chief Executive Officer 1999-02-15
Duffy Terri Vice President of Engineering 1998-03-03
Tamburello Roberto Engineering Manager 1997-12-12
…
…
Valdez Rachel Sales Representative 2003-07-01
Pak Jae Sales Representative 2002-07-01
Vakey Chudu Ranjit Sales Representative 2002-07-01
(290 row(s) affected)