Overview. Implementing Stored Procedures Creating Parameterized Stored Procedures Working With Execution Plans Handling Errors

Transcription

1 إعداد د. عبدالسالم منصور الشريف 1 Overview Implementing Stored Procedures Creating Parameterized Stored Procedures Working With Execution Plans Handling Errors 2 1

2 Lesson 1: Implementing Stored Procedures What Is a Stored Procedure? Syntax for Creating Stored Procedures Guidelines for Creating Stored Procedures Syntax for Altering and Dropping Stored Procedures 3 What Is a Stored Procedure? A named collection of Transact-SQL statements or Microsoft.NET Framework code Accepts input parameters and returns output parameter values Returns status value to indicate success or failure 4 2

3 Advantages of stored procedures Encapsulate business functionality and create reusable application logic. Shield users from exposure to the details of the tables in the database. Provide security mechanisms. Improve performance. Reduce network traffic. Reduce vulnerability to SQL injection attacks. 5 Syntax for Creating Stored Procedures Create in current database by using the CREATE PROCEDURE statement CREATE { PROC PROCEDURE } [schema_name.] procedure_name [ [ type_schema_name. ] data_type } [ VARYING ] [ = default ] [ [ OUT [ PUT ] ] [,...n ] [ WITH <procedure_option> [,...n ] sql_statement [;][...n ] <procedure_option> ::= Use EXECUTE to run stored procedure [ ENCRYPTION ] [ RECOMPILE ] [ EXECUTE Clause ] 6 3

4 Syntax for Creating Stored Procedures Create in current database by using the CREATE PROCEDURE statement CREATE PROCEDURE Production.LongLeadProducts SELECT Name, ProductNumber FROM Production.Product WHERE DaysToManufacture >= 1 Use EXECUTE to run stored procedure EXECUTE Production.LongLeadProducts 7 Guidelines for Creating Stored Procedures Qualify object names inside procedure Create one stored procedure for one task Create, test, and troubleshoot Avoid sp_ prefix in stored procedure names Use consistent connection settings for all stored procedures (SET QUOTED_IDENTIFIER and SET ANSI_NULLS) Minimize use of temporary stored procedures (created in the tempdb) 8 4

5 Syntax for Altering and Dropping Stored Procedures ALTER PROCEDURE ALTER PROC Production.LongLeadProducts SELECT Name, ProductNumber, DaysToManufacture FROM Production.Product WHERE DaysToManufacture >= 1 ORDER BY DaysToManufacture DESC, Name EXEC = N'Production.LongLeadProducts' DROP PROCEDURE DROP PROC Production.LongLeadProducts 9 Lesson 2: Creating Parameterized Stored Procedures Input Parameters Output Parameters and Return Values Practice: Creating a Parameterized Stored Procedure 10 5

6 Input Parameters Provide appropriate default values Validate incoming parameter values, including null checks ALTER PROC int = 1 -- default value IF (@MinimumLength < 0) -- validate BEGIN RAISERROR('Invalid lead time.', 14, 1) RETURN END SELECT Name, ProductNumber, DaysToManufacture FROM Production.Product WHERE DaysToManufacture ORDER BY DaysToManufacture DESC, Name EXEC 11 Output parameters CREATE PROCEDURE smallint OUTPUT = smallint EXECUTE MathTutor OUTPUT SELECT 'The result is: The result is:

7 Output parameters Create Procedure money OUTPUT As = sales FROM sample WHERE id 13 Output parameters CREATE PROCEDURE INT OUTPUT = COUNT(*) FROM Person.Contact WHERE LastName INT EXEC = OUTPUT SELECT TheCount 14 7

8 Output Parameters and Return Values CREATE PROC HumanResources.AddDepartment CREATE PROC smallint smallint OUTPUT IF = '') OR = '')) RETURN -1 INSERT INTO HumanResources.Department (Name, GroupName) INSERT INTO HumanResources.Department (Name, GroupName) = SCOPE_IDENTITY() SCOPE_IDENTITY() RETURN 0 - return single integer value (represent status) -- if no return specified then return 0 by default int EXEC = AddDepartment 'Refunds', 'Refunds', '', OUTPUT IF (@result = 0) ELSE SELECT 'Error during insert' 15 Lesson 3: Working With Execution Plans What Is an Execution Plan? Viewing an Execution Plan Execution Plan Caching Query Compilation Forcing Stored Procedure Recompilation 16 8

9 What Is an Execution Plan? Shows the actual or estimated execution of a query Performance and Optimization Table or index scans Bookmark lookups Filter Sort 17 Viewing an Execution Plan SQL Server Management Studio Open or type a Transact-SQL script Click Display Estimated Execution Plan or Include Actual Execution Plan button Query is parsed or executed Click the Execution plan tab Transact-SQL SET SHOWPLAN_XML ON SET SHOWPLAN_TEXT ON SET STATISTICS XML ON SET STATISTICS PROFILE ON 18 9

10 Execution Plan Caching Execution context connection 1 Parameter value: 12 Execution context connection 2 Parameter value: 24 Execution context connection 3 Parameter value: 36 Query plan SELECT * FROM MyTable WHERE PriKey =? Procedure cache Age Cost 19 Execution Plan 20 10

11 Query Compilation Parsing Normalization Compilation Optimization 21 Forcing Stored Procedure Recompilation Stored 1 sp_recompile procedure recompilation 2 3 WITH RECOMPILE at creation WITH RECOMPILE on execution USE AdventureWorks; EXEC sp_recompile N'Sales.Customer'; 22 11

12 Lesson 4: Handling Errors Syntax for Structured Exception Handling Guidelines for Handling Errors Practice: Handling Errors 23 Syntax for Structured Exception Handling TRY CATCH blocks provide the structure TRY block contains protected transactions CATCH block handles errors CREATE PROCEDURE int BEGIN TRY INSERT INTO TableWithKey END TRY BEGIN CATCH SELECT ERROR_NUMBER() ErrorNumber, ERROR_MESSAGE() [Message] END CATCH 24 12

13 Guidelines for Handling Errors Create CATCH block immediately after TRY Roll back failed transactions in CATCH BEGIN TRY -- INSERT INTO... END TRY SELECT * FROM TableWithKey -- NOT ALLOWED BEGIN CATCH TRY -- BEGIN SELECT TRANERROR_NUMBER() END CATCH INSERT... SET XACT_ABORT ON INSERT... BEGIN Capture TRY ERROR_xxx information if required COMMIT TRAN BEGIN TRAN END TRY... BEGIN CATCH BEGIN COMMIT TRAN ROLLBACK TRY TRAN END... TRY SELECT MESSAGE_NUMBER... END BEGIN CATCH TRY CATCH BEGIN IF (XACT_STATE()) CATCH = uncommitable INSERT ROLLBACK INTO TRAN ErrorLog ELSE VALUES IF (XACT_STATE()) (ERROR_NUMBER(), = 1ERROR_MESSAGE(), -- commitable GETDATE()) END CATCH COMMIT TRAN END CATCH Consider using XACT_ABORT ON and XACT_STATE 25 Handling Errors CREATE TABLE dbo.tablenokey(cola int, ColB int) CREATE TABLE dbo.tablewithkey(cola int PRIMARY KEY, ColB int) CREATE PROCEDURE int BEGIN TRY INSERT dbo.tablenokey VALUES INSERT dbo.tablewithkey VALUES END TRY BEGIN CATCH SELECT ERROR_NUMBER() ErrorNumber, ERROR_MESSAGE() [Message] END CATCH EXEC dbo.adddata 1, 1 EXEC dbo.adddata 2, 2 EXEC dbo.adddata 1, error duplicate key 26 13

14 Handling Errors SET XACT_ABORT ON BEGIN TRY BEGIN TRAN... COMMIT TRAN END TRY BEGIN CATCH IF (XACT_STATE()) = uncommittable ROLLBACK TRAN ELSE IF (XACT_STATE()) = 1 -- committable COMMIT TRAN END CATCH 27 14