STORE PROCEDURESTORE PROCEDURE

PRESENTATION

Presented By – Amin Uddin

Overview• About Store Procedure • Difference between SP and Function• How to create a store procedure• How to call.• Initial Processing - Review

ResolutionCompilation/OptimizationExecution/Recompilation

• Recompilation Issues When do you want to Recompile?Options for Recompilation? What to Recompile?

What is store procedure?• A stored procedure is a set of SQL commands that has been compiled and stored on the database server.

Once the stored procedure has been "stored", client applications can execute the stored procedure over and over again without sending it to the database server again and without compiling it again.

Stored procedures improve performance by reducing network traffic and CPU load.

Comparison with dynamic SQL

• Remove overhead•Avoidance of network traffic•Encapsulation of business logic•Delegation of access-rights•Some protection from SQL injection attacks

Comparison with functions• 1.Procedure can return zero or n values whereas function can return one

value which is mandatory.

2.Procedures can have input,output parameters for it whereas functions can have only input parameters.

3.Procedure allow select as well as DML statement in it whereas function allow only select statement in it.

4.Functions can be called from procedure whereas procedures cannot be called from function.

5.Exception can be handled by try-catch block in a procedure whereas try-catch block cannot be used in a function.

6.We can go for transaction management in procedure whereas we can't go in function.

7.Functions can run an executable file from SQL SELECT or an action query.operating system use Execute or Exec to run

How To Create And Execute SP

There are various options that can be used to create stored procedures.  In these next few topics we will discuss creating a stored procedure and How to execute.

Syntax Of Store ProcedureWith Parameter

-- =============================================-- Author: <Author,,Name>-- Create date: <Create Date,,>-- Description:<Description,,>-- =============================================Create Proc SP_Name(

Param1 DataType,param2 DataType,Param3 DataType,...Paramn DataType

)As

BeginBody Of Store Procedure

End

Implementation:-- =============================================

-- Author: <Author: XYZ>-- Create date: <Create Date:23/06/2010>-- Description: < Used to retrieve all information of an

employee Information of from the Table ‘EmployeeInfo’ according to supplied Employee ID>-- =============================================Create Proc SP_FetchSpecificEmployeeInfo(

EmpId verchar(50))As

BeginSelect * from EmployeeInfo where EmployeeID=

EmpIdEnd

-- =============================================-- Author: <Author,,Name>-- Create date: <Create Date,,>-- Description:<Description,,>-- =============================================

Create Proc SP_NameAsBegin

Body Of Store ProcedureEnd

Syntax Of Store Procedure

With out Parameter

Implemetaion-- =============================================

-- Author: <Author: XYZ>-- Create date: <Create Date:23/06/2010>-- Description: < Used to retrieve all information of the

table ‘EmployeeInfo’ without any Condition>-- =============================================Create Proc SP_FetchAllEmployeeInfo As

BeginSelect * from EmployeeInfo

End

Using SP How To Insert Information

-- =============================================-- Author: < XYZ>-- Create date: <23/06/2010>-- Description: < Used To Insert Employee Information >

-- =============================================CREATE proc SP_InsertEmployeeInfo(

@ID varchar(20) ,@Name varchar (50) ,@Pin varchar(20),@Email varchar(50),@MobileNo varchar(20),@PhoneNo varchar(20),@MailingAddr varchar(500) ,@ParmanentAddr Varchar(500) ,@Sex varchar(10) ,@JoingDate smalldatetime ,@Post varchar(50)

)

ASBegin

if exists(Select ID From EmployeeInfo Where ID = @ID)Begin

return 0Endelse

BeginInsert into EmployeeInfo(

ID,Name,Pin,Email,MobileNo,PhoneNo,MailingAddr ,ParmanentAddr ,Sex,JoingDate,Post

)

values(

@ID,@Name,@Pin,@Email,@MobileNo,@PhoneNo,@MailingAddr ,@ParmanentAddr ,@Sex,@JoingDate,@Post

)End

Beginreturn 1

End

End

Using SP How To Update Information-- =============================================

-- Author: < XYZ>-- Create date: <3/06/2010>-- Description: <Used To Update Record Of EmployeeInfo Table >

-- =============================================CREATE proc SP_UpdateEmployeeInfo(

@ID varchar(20) ,@Name varchar (50) ,@Pin varchar(20),@Email varchar(50),@MobileNo varchar(20),@PhoneNo varchar(20),@MailingAddr varchar(500) ,@ParmanentAddr Varchar(500) ,@Sex varchar(10) ,@JoingDate smalldatetime ,@Post varchar(50)

)

ASBegin

if not exists(select id from EmployeeInfo where ID = @ID)Begin

return 0End

elseBegin

Update EmployeeInfosetName =@Name,Pin =@Pin,Email =@Email,MobileNo =@MobileNo,PhoneNo =@PhoneNo,MailingAddr = @MailingAddr,ParmanentAddr =@ParmanentAddr,Sex =@Sex,JoingDate =@JoingDate,Post =@Post

where ID =@IDreturn 1

End

End

Using SP How TO Delete Record -- =============================================

-- Author: < XYZ>-- Create date: <3/06/2010>-- Description: <Used To Delete Record From EmployeeInfo Table

>-- =============================================CREATE PROC SP_DeleteEmployeeInfo(

@id varchar(20))AS

Begin if not exists(select id from EmployeeInfo where id = @id)

Begin return 0

End else

Beginif exists(select * from EmployeeInfo where id = @id and

DeleteStatus = 0)Begin

return 1End

elseBegin

delete from EmployeeInfo where id = @idreturn 2

EndEnd

End

How To Execute SP• If in a SP , there is no parameter then it executes the following

way.• Syntax

EXEC SP_NAME Implementation

EXEC SP_FetchAllEmployeeInfo

• If in a SP, there is one or more parameters then it executes the following way.

• Syntax • EXEC SP_NAME PARAMETER_lIST Implementation EXEC SP_FetchAllEmployeeInfo ‘001’

How To Perform Execute SP

Processing of Stored Procedures

Compiled plan placed inunified cache

Compiled plan placed inunified cacheCompilationCompilation

Execution(first time

or recompile)

Execution(first time

or recompile)

Resolution*Resolution*

OptimizationOptimization

ParsingParsing

ResolutionResolutionCreationCreation

sysobjectsName, type, etc.

syscomments Text of objectsyscolumns

Parameter listsysdepEnds

Object depEndencies

sysobjectsName, type, etc.

syscomments Text of objectsyscolumns

Parameter listsysdepEnds

Object depEndencies

Initial Steps• When a stored procedure is created all objects

referenced are resolved (checked to see whether or not they exist).

• The create will succeed even if the objects do not exist Procedures called that do not exist generate error

Cannot add rows to sysdepEnds for the current stored procedure because it depEnds on the missing object 'missingobjectname'. The stored procedure will still be created.Benefit: Recursion is allowed!

Tables, Views, Functions called that do not exist - do NOT generate error (unless in 6.5 compatibility mode)

• Verify depEndencies with sp_depEnds before dropping an object

Storing and Executing Procedures

When you create a stored procedure, the server stores the text of the procedure in the syscomments table of the current database. In addition, form of the procedure, called a query tree , in the sysprocedures table. The server uses the query tree to create a query plan and then execute.

Building the Query Tree: ResolutionThe process of building a query tree is called resolution. This process parses the SQL into a more efficient format and resolves all objects representations.

For example, table names are resolved into their object IDs and column names are resolved into their column IDs.

Building the Query Plan: Compilation

The process of building a query plan is called compilation. Adaptive Server builds a query plan on the first execution of a stored procedure. Adaptive Server reads the corresponding query tree from the sysprocedures table and loads it into the procedure cache. The server then creates procedure cache. The query plan is the optimized data access path that Adaptive Server uses to execute the procedure.

Adaptive Server determines the optimal data access path and builds the query plan based on the following information:

• The SQL stored in the query tree• Statistics for each table and index referenced • in the procedure

•The values of any parameters passed to the procedure on the first execution.

Multiple Users and the Query PlanStored procedures are reusable, not reentrant. This means that

only one user at a time can execute a given copy of a procedure's query plan. the same procedure at the same time, Adaptive Server creates an additional query plan based on the parameters used in the later execution.

procedure, the query plan is available in cache for reuse by anyone with execute permissions.

If the server must generate a second query plan for a stored procedure, there is no guarantee that it is the same as the first.

When to recompile? When the plan for a given statement within a

procedure is not consistent in execution plan – due to parameter and/or data changes

Cost of recompilation might be significantly less than the execution cost of a bad plan!Why?

Faster Execution with a better plan Saving plans for reuse is NOT always

beneficial Some plans should NEVER be saved

Recompilation IssuesRECOMPILATION = OPTIMIZATION

OPTIMIZATION = RECOMPILATION

When do you want to recompile? What options do you have Recompilation? How do you know you need to recompile? Do you want to recompile the entire

procedure or only part of it? Can you test it?

Procedure RecompilationThe process of building a query plan is called compilation. Recompilation is the creation of a new query plan from the existing query tree. one of the following events occurs:

•The procedure is loaded from disk to the procedure cache.

• You drop an index on any table referred to in the procedure.

• All copies of the execution plan in cache are currently in use and another user wants to execute the procedure.

• You execute a procedure using the with recompile option.

Procedure Re-resolutionLike recompilation, re-resolution causes the generation of a new plan. In addition, re-resolution updates the existing query tree in theRe-resolution occurs when one of the tables changes in such a way that the query tree stored in the sysprocedures table may be invalid. IDs, or other parts of the table may have changed. In this case, Adaptive Server must rebuild some parts of the query tree.

Adaptive Server re-resolves procedures after you do any of the following:

• Execute the procedure for the first time after a load database.

• Drop and re-create any table used or referenced by the procedure.

• Drop and re-create a database containing a referenced table.

• Bind or unbind a default or rule to a table referred to by a query in the procedure.

Options for Recompilation CREATE … WITH RECOMPILE

When procedure returns widely varying resultsWhen the plan is not consistent

EXECUTE … WITH RECOMPILEFor testing and to determine if CREATE WITH

RECOMPILE is necessary sp_recompile objname

Forces all plans with regard to that object to be invalidated (note: this does not force recompilation on views even though a view name is supported)

Statement Recompilation Dynamic String Execution or Modularized Code

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Thanks