1. 8/6/2015 1 ITE 370: SQL Stored Procedures

2. 8/6/2015 2 Stored Procedures A stored procedure is A stored procedure is a collection of SQL statements saved under a name and processed by the database server as a unit a collection of SQL statements saved under a name and processed by the database server as a unit Stored procedures Stored procedures are precompiled and ready for later use are precompiled and ready for later use can take and return user-supplied parameters can take and return user-supplied parameters may contain control-of-flow statements (conditionals, loops) may contain control-of-flow statements (conditionals, loops) are created, modified, called, tested using SQL-Server are created, modified, called, tested using SQL-Server

3. 8/6/2015 3 Advantages of Stored Procedures Reuse Reuse write once, call many write once, call many can be shared by multiple users of db can be shared by multiple users of db Convenient means of abstraction Convenient means of abstraction Easier to write than SQL embedded within VB Easier to write than SQL embedded within VB Centralizes access to data Centralizes access to data More secure means of data access More secure means of data access Fast execution Fast execution precompiled SQL statements precompiled SQL statements cached results (Results are stored temporarily) cached results (Results are stored temporarily)

4. 8/6/2015 4 Disadvantages of Stored Procedures Extra layer of hidden complexity on top of SQL statements Extra layer of hidden complexity on top of SQL statements Can be used to restrict application and user access to data Can be used to restrict application and user access to data Programming environment not as advanced as modern, visual IDEs Programming environment not as advanced as modern, visual IDEs Fewer advanced code writing, testing, debugging features available in SQL-Server Fewer advanced code writing, testing, debugging features available in SQL-Server No search and replace No search and replace

5. 8/6/2015 5 Stored Procedure Syntax – SQL Server CREATE PROC [ EDURE ] procedure_name [ { @parameter data_type } [ = default ] [ OUTPUT ] ] [,...n ] AS sql_statement [...n ]

6. 8/6/2015 6 Example – Create a stored proc in SQL-Server Write this in the SQL Server Management Studio Query Builder and run to create a new stored procedure: Write this in the SQL Server Management Studio Query Builder and run to create a new stored procedure: CREATE PROCEDURE GetStopsOnRoute @RouteId int AS SELECT * FROM StopOnRoute WHERE RouteId=@RouteId

7. 8/6/2015 7 Same Example, More Detail CREATE PROCEDURE dbo.GetStopsOnRoute -- returns a chronological listing of bus stops on a given bus route @RouteId int -- PK of a bus route to list AS BEGIN -- sproc -- retrieve information for all Stops on the given bus route, listed -- in chronological order SELECT RouteId, StopOnRouteId, Stop.StopId, Location, ElapsedTime, Outbound FROM StopOnRoute INNER JOIN Stop ON StopOnRoute.StopId=Stop.StopId Stop ON StopOnRoute.StopId=Stop.StopId WHERE RouteId=@RouteId ORDER BY ElapsedTime END -- sproc -- example call for RouteId=2 (written seperately in the query builder) -- EXEC dbo.GetStopsOnRoute 2 -- execute script GO

8. 8/6/2015 8 Stored Proc Example with Insert CREATE PROCEDURE dbo.InsertStop -- adds a new row to the table of bus stops @Location nvarchar(50), -- location of new bus stop to insert @Shelter bit, -- shelter of stop to insert; 1=has shelter, 0=not @Seating nvarchar(25) -- type of seating (bench, multi-seat) of stop AS BEGIN-- sproc INSERT INTO Stop (Location, Shelter, Seating) VALUES (@Location, @Shelter, @Seating) END-- sproc -- example call to insert a new bus stop row (written as separate query) -- EXEC dbo.InsertStop 'Ladd-Peebles Stadium', 1, 'Multi-Seat' -- verify that row was added by searching for it -- SELECT * FROM Stop WHERE Location LIKE 'Ladd%' -- note the % is SQL- Server wild-card -- execute the script GO

9. 8/6/2015 9 Example: Calling a stored proc

10. 8/6/2015 10 Modifying Stored Procs in SQL- Server Use the ALTER PROCEDURE command Use the ALTER PROCEDURE command Instead of CREATE Instead of CREATE Because the sproc already exists Because the sproc already exists Script stored under Properties Script stored under Properties Paste into the Query Analyzer Paste into the Query Analyzer Edit, run, debug, run Edit, run, debug, run Remember to Refresh in Enterprise Manager Remember to Refresh in Enterprise Manager Scripts can be stored locally as text files with.sql default extension Scripts can be stored locally as text files with.sql default extension

11. 8/6/2015 11 Declaring Local Variables Syntax: Syntax: DECLARE {{ @local_variable data_type } } [,...n] Example: Example: DECLARE @StopCount int, @LastName nvarchar(20) @LastName nvarchar(20)

12. 8/6/2015 12 Assigning Values to Local Variables Syntax: Syntax: SET { { @local_variable = expression } } Examples: Examples: SET @LastName = ‘Manning’ SET @StopCount = 42 SET @HR = (SELECT Sum(HR) FROM Player)

13. 8/6/2015 13 Stored Procs with Output Parameter ALTER PROC dbo.GetNumOfStopsOnRoute @RouteId int, @StopCount int OUTPUT AS SET @StopCount = (SELECT Count(*) AS Stops SET @StopCount = (SELECT Count(*) AS Stops FROM StopOnRoute FROM StopOnRoute WHERE RouteId=@RouteId) WHERE RouteId=@RouteId) -- example call to retrieve number of stops on RouteId=1 /* DECLARE @NumOfStops int DECLARE @NumOfStops int SET @NumOfStops = 0 SET @NumOfStops = 0 EXEC dbo.GetNumOfStopsOnRoute 1, EXEC dbo.GetNumOfStopsOnRoute 1, @StopCount = @NumOfStops OUTPUT @StopCount = @NumOfStops OUTPUT SELECT @NumOfStops AS TotalStops SELECT @NumOfStops AS TotalStops*/GO