Sql xp 09

Implementing Stored Procedures

Objectives
In this lesson, you will learn to:
Create a stored procedure
Execute a stored procedure
Pass parameters to a stored procedure
Modify a stored procedure
Return values from a stored procedure
Return multiple values from a stored procedure
Call a procedure from another stored procedure
Recompile a stored procedure
Drop a stored procedure
©NIIT SQL/Lesson 9/Slide 1 of 61


Getting Started
A stored procedure is a collection or batch of T-SQL
statements and control-of-flow language that is stored under
one name, and executed as a single unit
Benefits of Stored Procedures
Improved performance
Reduction in network congestion
Better consistency
Better security mechanism



Getting Started (Contd.)
Types of Procedures
User-defined
System
Temporary
Remote
Extended



Just a Minute…
What are the benefits of using stored procedures?



9.D.1 Speeding up the Execution of Batch Statements
A list containing the name, address, city, zip code, telephone
number, and the fax number of recruitment agencies is
required frequently. Recently, it has been noticed that there
is a delay in generating this report due to the network
congestion. Besides, the Human Resources department
personnel make mistakes while querying for this information.
Suggest and implement a solution.



Task List
Identify the object that can be used to solve the above
problem
Draft the stored procedure on paper
Create the stored procedure in the database
Check the existence of the procedure in the database
Execute the procedure



Identify the object that can be used to solve the above
Problem
Result:
Use a stored procedure to reduce network traffic and reduce
the errors committed by the HR personnel



Draft the stored procedure on paper
The CREATE PROCEDURE Statement
Syntax
CREATE PROCEDURE proc_name
AS
BEGIN
sql_statement1
sql_statement2
END



Draft the stored procedure on paper (Contd.)
Result:
The database in which the stored procedure has to be
created is Recruitment
The type of procedure is user-defined
The name for the stored procedure is
prcPrintRecruitmentAgencyList


Action:
In the Query Analyzer window, type:
CREATE PROCEDURE
AS
BEGIN
PRINT 'List of Recruitment Agencies'
SELECT cName, vAddress, cCity, cZip,
cPhone, cFax
FROM RecruitmentAgencies
END
Press F5 to execute the statement



The sp_helptext Command is used to check the existence of
a procedure in the database
Syntax
sp_helptext proc_name
Action
sp_helptext prcPrintRecruitmentAgencyList
Check the result. The output must be the code that you
wrote to create the procedure



The EXECUTE PROCEDURE statement is used to execute
the stored procedure
Syntax
EXECUTE proc_name
or
EXEC proc_name
or
proc_name



Execute the procedure (Contd.)
Action:
EXECUTE prcPrintRecruitmentAgencyList
or
EXEC prcPrintRecruitmentAgencyList
or
Press F5 to execute the command



Just a Minute…
The query to obtain the list of candidates and their
recruitment agencies is:
SELECT 'Candidate Name' = vFirstName ,
'Recruitment Agency' = cName
FROM ExternalCandidate
JOIN RecruitmentAgencies
ON ExternalCAndidate.cAgencyCode =
RecruitmentAgencies.cAgencyCode
Create a stored procedure for the same.



9.D.2 Creating a Generic Stored Procedure
Information on contract recruiters in a particular city is
required frequently.The city for which details are required
changes from time to time. Create a stored procedure that
will generate information for a specified city



Task List
Identify a method to write a generic procedure that will
generate results for variable inputs
Draft statements to create a procedure
Prepare test cases with existing and non-existing values
Execute the procedure with the existing value
Execute the procedure with the non-existing value



Identify a method to write a generic procedure that
will generate results for variable inputs
Parameter
A parameter is a placeholder in a query or a stored
procedure that accepts a user-defined value whenever
the query or stored procedure is executed
Types of Parameters
Input parameters
Output parameters
Result:
As the city name will be supplied by the user, use input
parameters



Draft statements to create a procedure
Result:
The variable name is @cCity
The datatype of the variable is char of size 15. So, the
variable needs to be declared, as shown below:
@cCity char(15)



Action:
CREATE PROC prcListContractRecruiter
@cCity char(15)
AS
BEGIN
PRINT 'List of Contract Recruiters'
SELECT cName,cCity,cZip,cPhone
FROM ContractRecruiter
WHERE cCity = @cCity
END
Press F5 to execute the query


Action:
sp_helptext prcListContractRecruiter
Check the result
Prepare test cases with the existing and non-existing
values
Action:
Test for a city, which exists in the ContractRecruiter table:
Alexandria
Test for a city, which does not exist in the ContractRecruiter
table: Boston


Execute the procedure with the existing value
Action:
prcListContractRecruiter Alexandria
Press F5 to execute the procedure
Execute the procedure with the non-existing value
Action:
prcListContractRecruiter Boston
Press F5 to execute the procedure



9.D.3 Modifying a Stored Procedure
Details of the recruitment agencies for a particular city are
required. The city for which the data is required varies from
time to time. Instead of creating a new procedure, modify the
existing prcPrintRecruitmentAgencyList procedure to meet
this requirement. In the new procedure, if no value is passed
to the procedure, it should display 'Usage:
prcPrintRecruitmentAgencyList city' and stop execution.



Task List
Identify a method to modify the existing procedure
Draft statements to modify a procedure
Verify that the procedure has been modified



The ALTER PROCEDURE Statement is used to modify an
existing procedure.
The Default Parameter
You can use default parameters to pass value to the
stored procedure in case no value is passed to it.
The value passed as default value must be a constant
value or NULL.
Result:
Use the ALTER PROCEDURE statement to modify the
procedure.



(Contd.)
Use NULL as the default parameter to the procedure. If
no value is passed to the procedure parameter, the
parameter would contain a NULL value. If the value of the
parameter is NULL, the procedure should display a
message explaining the usage of the procedure.
Draft statements to modify a procedure
Action:
ALTER PROCEDURE prcPrintRecruitmentAgencyList
@city char(15)=NULL



Draft statements to modify a procedure (Contd.)
AS
BEGIN
IF @city is null
BEGIN
PRINT 'Usage:
prcPrintRecruitmentAgencyList city'
RETURN
END
SELECT cName,vAddress,cZip,cPhone
WHERE cCity = @city
©NIIT
END SQL/Lesson 9/Slide 26 of 61


Draft statements to modify a procedure (Contd.)
In the above code, the RETURN statement passes the
control back to the position from where it was called



Verify that the procedure has been modified
Action:
sp_helptext prcPrintrecruitmentAgencyList
Action:
EXEC prcPrintRecruitmentAgencyList
Alexandria


Execute the procedure (Contd.)
In case you do not pass any parameter to the procedure
by typing:
you will get the following output:
Usage: prcPrintRecruitmentAgencyList
city



9.D.4 Notifying Successful Execution
Modify the prcPrintRecruitmentAgencyList procedure to
notify users of its successful execution



Task List
Identify a method to write a procedure that will return a value
Draft the procedure
Modify the procedure in the database
Check that the procedure has been modified in the database



Identify a method to write a procedure that will return
a value
The RETURN Keyword
You use the RETURN statement to return values from a
stored procedure
Syntax
RETURN value
Result:
The RETURN statement can be used to return values from a
stored procedure



Draft the procedure
Result:
The batch statements for creating the stored procedure
are as follows:
ALTER PROCEDURE
prcPrintRecruitmentAgencyList @city
char(15)
AS
BEGIN
IF EXISTS(SELECT * FROM RecruitmentAgencies

WHERE cCity=@city)


Draft the procedure (Contd.)
BEGIN
SELECT cName,vAddress,cZip,cPhone
WHERE cCity = @city
Return 0
END
ELSE BEGIN
PRINT 'No Records Found for given city' RETURN 1
END
END


Modify the procedure in the database
Action:
In the Query Analyzer window, type



Check that the procedure has been modified in the
database
Action:
sp_helptext



Action:
DECLARE @ReturnValue int
EXEC @ReturnValue =
prcPrintRecruitmentAgencyList 'Alexandria'
SELECT @ReturnValue
Press F5 to execute the statement. When the above
statements are executed, the value returned by the
procedure prcPrintRecruitmentAgencyList would be
stored in the variable @ReturnValue. This value would be
displayed by the SELECT statement


9.D.5 Calling One Procedure From Another
Details about the recruitment agencies and the contract
recruiters in a city are required in a single report. Create a
single procedure that uses the existing procedures for the
report



Task List
Create the procedure in the database
Execute the procedure with parameters



Identify a method to write a procedure that will use an
existing procedure
Nested Procedures
You can execute or call one procedure from within
another procedure
Result:
Create a new stored procedure that will call the existing
procedures



Action:
CREATE PROCEDURE prcDisplayBoth
@city char(15)
AS
BEGIN
EXEC prcListContractRecruiter @city
EXEC prcPrintRecruitmentAgencyList @city
END



Action:
sp_helptext prcDisplayBoth

Action:
prcDisplayBoth 'Alexandria'



Just a Minute…
You need to modify a stored procedure. Which command will
you use to modify the procedure?



9.D.6 Returning Multiple Output Values
A formatted report of the status of positions available in
the company is to be displayed. Create a procedure,
prcGetPositionDetail which will return the position
description, the budgeted manpower and the current
strength of employees for a given position. Create another
procedure called prcDisplayPositionStatus that will display
cRequisitionCode, vRegion, and siNoOfVacancy from the
Requisition table. The procedure prcDisplayPositionStatus
should also call the prcGetPositionDetail procedure and
display the values returned by it for position '0002' in the
following format:



9.D.6 Returning Multiple Output Values (Contd.)
The Status for the Position: Maketing Manager

Budgeted Strength : 100

Current Strength : 83

cRequisitionCode vRegion siNoOfVacancy
---------------- -------------------- ----------
000002 Texas 11



Task List
Identify a method to write a generic procedure that will return
more than one value
Check whether the procedure exists in the database



Identify a method to write a generic procedure that
will return more than one value
The OUTPUT Parameter - is used to return more than one
value from the procedure
Syntax
CREATE PROC[EDURE] procedure_name
[ {@parameter data_type} [OUTPUT]
]
AS
sql_statement [...n]
Result:
® Use CREATE PROCEDURE with the OUTPUT option



Action:
In the Query Analyzer Window, type the statements given
below.
CREATE PROCEDURE prcGetPositionDetail
@Pcode char(4),
@Description char(30) OUTPUT,
@budget int OUTPUT,
@CurrentStrength int OUTPUT
AS
BEGIN
IF EXISTS(SELECT * FROM Position WHERE
cPositionCode = @PCode)


Create the procedure in the database (Contd.)
BEGIN
SELECT @Description =
vDescription,@budget =
iBudgetedStrength,
@CurrentStrength = iCurrentStrength
FROM Position
WHERE cPositionCode=@Pcode
RETURN 0
END
ELSE
RETURN 1
END
Press F5 to execute


In the Query Analyzer Window, type:
CREATE PROCEDURE prcDisplayPositionStatus
@PCode char(4)
AS
BEGIN
DECLARE @Description char(30)
DECLARE @budget int
DECLARE @CurrentStrength int
DECLARE @ReturnValue int
EXEC @ReturnValue = prcGetPositionDetail
@Pcode,
@Description output,
@Budget output,
@CurrentStrength output


IF (@ReturnValue = 0)
BEGIN
PRINT 'The Status for the Position: '
+ @Description
PRINT 'Budgeted Strength : ' +
CONVERT( char(30), @budget)
PRINT 'Current Strength : ' + CONVERT
(char(30), @CurrentStrength)
SELECT cRequisitionCode,vRegion,
siNoOfVacancy FROM Requisition WHERE
cPositionCode=@Pcode


END
ELSE
PRINT 'No records for the given position
code'
END
Press F5 to execute



Check whether the procedure exists in the database
In the Query Analyzer window, type and execute the
following statements:
sp_helptext prcGetPositionDetail
go
sp_helptext prcDisplayPositionStatus
go



Action:
prcDisplayPositionstatus '0002'
Press F5 to execute
Verify that the required output is displayed



The RECOMPILE Option
To generate an updated execution plan, you must recompile
the stored procedure, each time you execute the stored
procedure
Syntax
CREATE PROCEDURE proc_name [WITH RECOMPILE]
AS
sql_statements



The DROP PROCEDURE Statement
Is used to drop a stored procedure from the database
Syntax
DROP PROCEDURE proc_name
You cannot retrieve a procedure once it is dropped



Extended Stored Procedures
Allow you to create your own external routines in a
programming language such as C
Are Dynamic-Link Libraries (DLLs) that SQL Server can
dynamically load and execute



Summary
In this lesson, you learned that:
A stored procedure is a collection of various T-SQL statements
that are stored under one name and executed as a single unit
A stored procedure can be created either in the Enterprise
Manager or in the Query Analyzer window with the CREATE
PROCEDURE statement
A stored procedure allows you to declare parameters, variables,
and use T-SQL statements and programming logic
A stored procedure provides better performance, security, and
accuracy, and reduces network congestion



Summary (Contd.)
The various types of stored procedures are:
User-defined
System
Temporary
Remote
Extended
A stored procedure accepts and returns data through the
following:
Input parameters


Summary (Contd.)
Output parameters
Return statements
A stored procedure can be executed using the EXECUTE
statement
A stored procedure can be altered using the ALTER
PROCEDURE statement

A stored procedure can be viewed using the sp_help and the
sp_helptext system procedures
To generate an updated execution plan, you must recompile
the stored procedure each time you execute the stored
procedure


Summary (Contd.)
To recompile a stored procedure automatically, you must create
the stored procedure with a WITH RECOMPILE option
A stored procedure can be dropped using the DROP
PROCEDURE statement
Extended stored procedures are Dynamic-Link Libraries (DLLs)
that SQL Server can dynamically load and execute


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