STORED PROCEDURES AND FUNCTION (9.6.1) Chapter 9 (tt) STORED PROCEDURES AND FUNCTION (9.6.1)

Introduction Stored procedure (SP): is a segment of code which contains declarative or procedural SQL statements. A stored procedure is resided in the catalog of the database server so we can call it from a trigger, another stored procedure or even from client applications. Stored procedures are essentially functions that you can create in the database and reuse. They can take input parameters and then return a result

Stored procedures type System SP (sp): is stored in the Master database, but can be executed in any database without using its full name. sp_helptext: Prints the text of a rule, a default, or an unencrypted stored procedure, user-defined function, trigger, computed column, or view. Example : master.dbo.sp_helptext sp_help: Reports information about a database object sp_depends: Displays information about database object dependencies the view(s), trigger(s), and procedure(s)—in the database that depend on a specified table or view,

Stored procedures type Extended SP (xp): is created from other languages (C++,...) and used as a procedure of SQL Server User_defined : Local sp: is an object in the database to execute the tasks. It can be created in master db. Temporary sp: local (with the name begun by #) and global (with the name begun by ##).

Create stored procedures Syntax: CREATE PROC [ EDURE ] procedure_name [ ; number ] [ { @parameter data_type } [ VARYING ] [ = default ] [ OUTPUT ] ] [,...n ] [ WITH  { RECOMPILE | ENCRYPTION | RECOMPILE, ENCRYPTION } ] [ FOR REPLICATION ] AS sql_statement [ ...n ]

Create stored procedures Example: CREATE PROCEDURE OrderSummary AS SELECT Ord.EmployeeID, SummSales=SUM(OrDet.UnitPrice*OrDet.Quantity) FROM Orders AS Ord JOIN [Order Details] AS OrDet ON (Ord.OrderID = OrDet.OrderID) GROUP BY Ord.EmployeeID

Execute stored Procedures Execute: Executes user-defined function, a system procedure, a user-defined stored procedure, or an extended stored procedure. Syntax: [ [ EXEC [ UTE ] ] {[ @return_status = ]     { procedure_name [ ;number ] | @procedure_name_var     }     [ [ @parameter = ] { value | @variable [ OUTPUT ] | [ DEFAULT ] ] [,...n ] [ WITH RECOMPILE ]

Execute stored Procedures Example: EXECUTE dbo.overdueOrders EXECUTE ProductName [ ; number ] [<parameter>[, …n][ OUTPUT ]]

Modify stored Procedures Syntax: ALTER PROCEDURE procedure_name [WITH option] AS sql_statement [...n]

Modify stored Procedures Example: ALTER PROC dbo.overdueOrders AS SELECT CONVERT(CHAR(8), RequiredDate,1) RequiredDate, CONVERT(CHAR(8), orderDate,1) orderDate, orderId, Customerid, EmployeeID FROM dbo.orders WHERE RequiredDate<GETDATE()and shippeddate is null ORDER BY RequiredDate

Delete stored Procedures Syntax: DROP PROC owner.stored_procedure_name

Using parameter in stored Procedures Input parameter: CREATE PROCEDURE procedure_name [@parameter_name data_type] [=default_value] [WITH option] AS sql_statement [...n]

Using parameter in stored Procedures Example 1: CREATE PROC dbo.MovieByRating @rating varchar(5) = NULL AS SELECT rating , title FROM movie WHERE rating = @rating ORDER BY title

Using parameter in stored Procedures Example 2 : CREATE PROC sp_name @parameter data_type =value AS IF @parameter IS NULL BEGIN PRINT ‘Message Line 1’ PRINT ‘Message Line 2’ RETURN END SELECT statement GO

Using parameter in stored Procedures Output parameter: CREATE PROCEDURE procedure_name [@parameter_name data_type] [=default_value] OUTPUT [WITH option] AS sql_statement [...n]

Using parameter in stored Procedures Example: CREATE PROC count_row @movie_count int OUTPUT AS SELECT @movie_count = COUNT(*) FROM Movie GO Sp execution with output parameter: a variable must be declared to stored the return value of the output parameter DECLARE @num int EXEC count_row @num OUTPUT SELECT @num

Errors management sp_addmessage: Stores a new user-defined error message in an instance of the SQL Server Database Engine. Messages can be viewed by using the sys.messages. Syntax: sp_addmessage [ @msgnum= ] msg_id , [ @severity= ] severity , [ @msgtext= ] 'msg' [ , [ @lang= ] 'language' ] [ , [ @with_log= ] { 'TRUE' | 'FALSE' } ] [ , [ @replace= ] 'replace' ]

Errors management Example: Create an error message by sp_addmessage EXEC sp_addmessage @msgnum = 50001, @severity = 10, @msgtext=‘Cannot delete customer. Customer has orders .’, @withlog = ‘true’ GO

Errors management VD: Display an error message when delete a customer CREATE PROC DeleteCust @cust_num nvarchar(5) = null AS IF EXISTS (SELECT customerID FROM Orders WHERE customerID like @cust_num) BEGIN RAISERROR (50001, 10, 1) RETURN END DELETE FROM Customers WHERE customerID like @cust_num GO

Errors management @@ERROR: Returns an error number if the previous statement encountered an error. Example: USE AdventureWorks2008R2; GO UPDATE HumanResources.EmployeePayHistory SET PayFrequency = 4 WHERE BusinessEntityID = 1; IF @@ERROR = 547 PRINT N'A check constraint violation occurred.';

Errors management @@ERROR and @@ROWCOUNT: Use to validate the operation of an UPDATE statement. The value of @@ERROR is checked for any indication of an error. The value of @@ROWCOUNT is used to ensure that the update was successfully applied to a row in the table.

FUNCTION System function: aggregate funtion: avg(), count(), count(*), sum(), max(), min(),... Other function: getdate(), month(), upper(), user_name(),@@rowcount,... User-defined function: Allow you to define your own T-SQL functions that can accept zero or more parameters and return a single scalar data value or a table data type.

FUNCTION There are 3 type User-defined function: Scalar: return a single value, based on the input value. Multi-statement Table-valued: return a set of row Inline Table-valued: return a set of row

FUNCTION Scalar function: CREATE  FUNCTION [ owner_name. ] function_name ( [ { @parameter_name [AS] scalar_parameter_data_type [= default ] } [ ,...n ] ] ) RETURNS scalar_return_data_type. [WITH < function_option> [ [,] ...n] ] [AS ] BEGIN     function_body     RETURN scalar_expression END

FUNCTION Example: CREATE FUNCTION dbo.OrderNum (@monthOrd tinyint ) RETURNS tinyint AS BEGIN DECLARE @Ordnum tinyint SELECT @Ordnum = count(orderid) FROM Orders WHERE month(orderdate)= @monthOrd RETURN @Ordnum END GO

FUNCTION Execute: SELECT dbo.OrderNum(7) Function can be used in the “Where” clause Select orderid from orders where dbo.OrderNum(7) > 50 and month(orderdate)=7

FUNCTION Table-valued Functions CREATE FUNCTION [ owner_name. ] function_name   ([{ @parameter_name [AS] scalar_parameter_data_type [= default ] } [,...n ] ]) RETURNS TABLE [WITH < function_option > [ [,] ...n ] ] [AS ] RETURN [(] select-stmt [)] Một hàm inline table-valued: Nó có thể được xem như là một View có tham số. Chúng thực thi một câu lệnh Select như trong một view nhưng có thể bao gồm các tham số, giống như thủ tục.

FUNCTION Example: CREATE FUNCTION SalesByCategory(@Categoryid Int) RETURNS TABLE AS RETURN (SELECT c.CategoryName, P. ProductName, SUM(Quantity) AS TotalQty FROM Categories c INNER JOIN Products p ON c.CategoryID= p. CategoryID INNER JOIN [Order Details] od ON p.ProductID = od.ProductID WHERE c.CategoryID= @Categoryid GROUP BY c. CategoryName,p.ProductName)

FUNCTION Multistatement Table-valuesd CREATE FUNCTION [owner_name.]function_name ([{@parameter_name [AS] data_type [=default]} [ ,…n ]]) RETURNS @return_variable TABLE ({column_definition | table_constraint} [ ,…n ]) [WITH { ENCRYPTION | SCHEMABINDING } [ [,] ...n] ] [AS] BEGIN function_body RETURN END

FUNCTION Example: CREATE FUNCTION Contacts(@suppliers bit=0) RETURNS @Contacts TABLE (ContactName nvarchar(30), Phone nvarchar(24), ContactType nvarchar(15)) AS BEGIN INSERT @Contacts SELECT ContactName, Phone, 'Customer' FROM Customers SELECT FirstName + ' ' + LastName, HomePhone, 'Employee' FROM Employees IF @Suppliers=1 SELECT ContactName, Phone, 'Supplier‘ FROM Suppliers RETURN END

FUNCTION Execute: SELECT * FROM CONTACTS(1) ORDER BY ContactName