Smart Database [Stored Procedures - Functions – Trigger]

Stored Procedures

• Benefits of Stored Procedures:

1. Precompiled execution

2. Reduced client/server traffic

3. Efficient reuse of code and programming abstraction

4. Enhanced security controls

• A stored procedure is an already written SQL statement that is saved in the database.

Functions

• Benefits of Functions :

1. Reusing code from one program to another, cutting down on program development time

2. Hiding the SQL details, allowing database developers to worry about SQL and application developers to deal only in higher-level languages

3. Centralize maintenance, allowing you to make business logic changes in a single place that automatically affect all dependent applications

Stored Procedures vs Functions

• A function is a subprogram written to perform certain computations and return a single value.

• Functions must return a value (using the RETURN keyword, but for stored procedures this is not compulsory).

• Stored procedures can use RETURN keyword but without any value being passed.

• Functions could be used in SELECT statements, provided they don’t do any data manipulation. However, procedures cannot be included in SELECT statements.

• A function can have only IN parameters, while stored procedures may have OUT or INOUT parameters.

• A stored procedure can return multiple values using the OUT parameter or return no value at all.

Trigger

• Triggers offer database developers and administrators a tremendous degree of flexibility. They are, quite simply, stored procedures that may be configured to automatically execute when certain events take place.

Stored Procedures Syntax

CREATE PROC[EDURE] [schema.]

procedure [ { @parameter [schema.]

data_type } [VARYING ] [ = default ]

[ OUT[PUT] ] ] [ ,...n ] [WITH Option

[,...n ]]

AS { sql_statement [;][ ...n ] | EXTERNAL

NAME assembly.class.method }

[;]

ALTER PROCEDURE

EXEC – Execute Procedure

DROP PROCEDURE

Functions Syntax

CREATE FUNCTION [schema.] function

( [@parameter [ AS ][type_schema.]

parameter_data_type [= default ]

[ ,...n ]

])

RETURNS return_clause...

[;]

ALTER FUNCTION

DROP FUNCTION

What Kind of User-Defined Functions ?

• There are three types of User-Defined functions in SQL Server and they are :

1. Scalar

2. Inline Table-Valued

3. Multi-statement Table-valued

Trigger DML

• Syntax for DML Trigger (INSERT, UPDATE, or DELETE)

CREATE TRIGGER [ schema.] trigger

ON { table | view }

[WITH trigger_option [ ,...n ] ]

{FOR | AFTER | INSTEAD OF}

{[INSERT] [, ] [UPDATE] [, ] [DELETE]}

[WITH APPEND ] [ NOT FOR REPLICATIO]

AS { sql_statement [;] [,...n] |

EXTERNAL NAME

assembly.class.method [;] }

Trigger DDL

• Syntax for DDL Trigger (CREATE, ALTER, DROP, GRANT, DENY, REVOKE, or UPDATE STATISTICS)

CREATE TRIGGER trigger

ON { ALL SERVER | DATABASE }

[WITH trigger_option [,...n] ]

{FOR | AFTER } { event_type |

event_group } [,...n]

AS { sql_statement [;] [,...n] |

EXTERNAL NAME

assembly.class.method [;] }

Related Trigger Commands :

• ALTER TRIGGER

• ENABLE TRIGGER

• DISABLE TRIGGER

• DROP TRIGGER

Stored Procedures Samples (1)

CREATE PROCEDURE [dbo].[GetProducts] AS

SELECT ProductID, ProductName FROM Products

-------------------------------------

EXEC GetProducts

Stored Procedured Examples (2)

CREATE PROCEDURE OrderSummary @MaxQuantity INT OUTPUT 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

ORDER BY Ord.EmployeeID

SELECT @MaxQuantity = MAX(Quantity) FROM [Order Details]

RETURN (SELECT SUM(Quantity) FROM [Order Details])

Stored Procedures Samples (3)

DECLARE @OrderSum INT

DECLARE @LargestOrder INT

EXEC @OrderSum = OrderSummary

@MaxQuantity = @LargestOrder OUTPUT

PRINT 'The size of the largest single order was: '

+ CONVERT(CHAR(6), @LargestOrder)

PRINT 'The sum of the quantities ordered was: '

+ CONVERT(CHAR(6), @OrderSum)

Stored Procedures Samples (4)

CREATE PROCEDURE CustomerOrder

@CustID nvarchar(5)

AS

SELECT orderID,CustomerId,OrderDate

FROM Orders

WHERE CustomerID=@CustID

-------------------------------------

EXEC CustomerOrder @CustID='WILMK'

Function Examples – Scalar (1)

CREATE FUNCTION whichContinent (@Country nvarchar(15))

RETURNS varchar(30)

AS

BEGIN

declare @Return varchar(30)

select @return = case @Country

when 'Argentina' then 'South America'

when 'Belgium' then 'Europe'

when 'Brazil' then 'South America'

when 'Canada' then 'North America'

when 'Denmark' then 'Europe'

when 'Finland' then 'Europe'

when 'France' then 'Europe'

else 'Unknown'

end

return @return

end

Function Examples - Scalar (2)

PRINT dbo.WhichContinent('USA')

-------------------------------------

SELECT dbo.WhichContinent(Customers.Country),

customers.* FROM customers

Function Examples – Scalar (3)

CREATE FUNCTION Job_Category(@Contact nvarchar(30))

RETURNS varchar(30)

AS

BEGIN

declare @return varchar(30)

select @return =

(case when @Contact like 'Owner%' then 'Owner'

else

(case when @Contact like 'Sales%' then 'Sales'

else

(case when @Contact like 'Marketing%' then 'Marketing'

else

(case when @Contact like 'Accounting%' then 'Accounting'

else 'Unknown'

END) END) END) END)

return @return

END

Function Examples – Scalar (4)

ALTER FUNCTION Price_Range(@Price money)

RETURNS varchar(30)

AS

BEGIN

declare @return varchar(30)

SELECT @return = case

when @Price<=0 then 'not for resale'

when @Price>0 AND @Price<=25 then 'under 25'

when @Price>25 AND @Price<=50 then 'under 50'

else 'over 50'

END

return @return

END

Function Examples - Inline Table-Valued (1)

CREATE FUNCTION CustomersByContinent

(@Continent varchar(30))

RETURNS TABLE

AS

RETURN

SELECT

dbo.WhichContinent(Customers.Country) as continent,

customers.*

FROM customers

WHERE dbo.WhichContinent(Customers.Country) =

@Continent

Function Examples - Inline Table-Valued (2)

SELECT * FROM CustomersbyContinent('North America')

SELECT * FROM CustomersByContinent('South America')

SELECT * FROM CustomersbyContinent('Unknown')

Function Examples - Multi-statement Table-valued (1) CREATE FUNCTION dbo.customersbycountry( @Country varchar(15)

)

RETURNS

@CustomersbyCountryTab table (

[CustomerID] [nchar] (5),

[CompanyName] [nvarchar] (40),

[ContactName] [nvarchar] (30),

[ContactTitle] [nvarchar] (30),

[Address] [nvarchar] (60),

[City] [nvarchar] (15),

[PostalCode] [nvarchar] (10),

[Country] [nvarchar] (15),

[Phone] [nvarchar] (24),

[Fax] [nvarchar] (24) )

AS

BEGIN

Function Examples - Multi-statement Table-valued (2)

INSERT INTO @CustomersByCountryTab

SELECT [CustomerID],

[CompanyName],

[ContactName],

[ContactTitle],

[Address],

[City],

[PostalCode],

[Country],

[Phone],

[Fax]

FROM [Northwind].[dbo].[Customers]

WHERE country = @Country

Function Examples - Multi-statement Table-valued (3)

DECLARE @cnt INT

SELECT @cnt = COUNT(*) FROM @customersbyCountryTab

IF @cnt = 0

INSERT INTO @CustomersByCountryTab (

[CustomerID],

[CompanyName],

[ContactName],

[ContactTitle],

[Address],

[City],

[PostalCode],

[Country],

[Phone],

[Fax] )

VALUES ('','No Companies Found','','','','','','','','')

RETURN

END

Function Examples - Multi-statement Table-valued (4)

SELECT * FROM dbo.customersbycountry('USA')

SELECT * FROM dbo.customersbycountry('CANADA')

SELECT * FROM dbo.customersbycountry('ADF')

Trigger Examples (1)

CREATE TABLE dbo.AuditTrail

( AuditTrailID Int IDENTITY (1, 1) NOT NULL,

TableName VarChar (50) NOT NULL,

ActionTaken Char (1) NOT NULL,

ActionUser VarChar (50) NOT NULL,

ActionDate DateTime NOT NULL

)

ON [PRIMARY]

Column Datatype NULL

AuditTrailID Identity Not allowed

TableName VarChar(50) Not allowed

ActionTaken Char(1) Not allowed

ActionUser VarChar(50) Not Allowed

ActionDate DateTime Not Allowed

Trigger Examples (2)

CREATE TRIGGER [AuditInsertUpdate] ON dbo.Products

FOR INSERT, UPDATE

AS

INSERT INTO AuditTrail (TableName, ActionTaken,

ActionUser, ActionDate)

VALUES ('Products', 'I', User_Name(), GetDate())

-------------------------------------

CREATE TRIGGER [AuditDelete] ON dbo.Products

FOR DELETE

AS

INSERT INTO AuditTrail (TableName, ActionTaken,

ActionUser, ActionDate)

VALUES ('Products', 'D', User_Name(), GetDate())

Trigger Examples (3)

UPDATE dbo.Products SET UnitPrice = 1

WHERE ProductID = 1

SELECT * FROM dbo.AuditTrail

Trigger - Inserted and Deleted tables

• DML trigger statements use two special tables: the deleted table and the inserted tables.

• The deleted table stores copies of the affected rows during DELETE and UPDATE statements

• The inserted table stores copies of the affected rows during INSERT and UPDATE statements

Trigger Examples (4)

CREATE TABLE [dbo].[TriggerTest]

([au_id] [int] NULL,

[au_name] [varchar] (50))

-------------------------------------

CREATE TRIGGER tr_InsertConcatName ON authors

FOR INSERT AS

DECLARE @AuthorID VARCHAR(11)

DECLARE @ConcatName VARCHAR(50)

SELECT @AuthorID = (SELECT au_id FROM Inserted)

SELECT @ConcatName = (SELECT au_lName + ', ' +

au_fName FROM Inserted)

INSERT TriggerTest values (@AuthorID,@ConcatName)

-------------------------------------

INSERT authors (au_id, au_lname, au_fname, contract)

VALUES ('123-45-6789', 'Woody', 'Buck', 1)

Trigger Examples (5)

CREATE TRIGGER tr_UpdateConcatName ON authors

FOR UPDATE AS

DECLARE @AuthorID VARCHAR(11)

DECLARE @NewConcatName VARCHAR(50)

SELECT @AuthorID = (SELECT au_id FROM Inserted)

SELECT @NewConcatName = (SELECT au_lName + ', ' +

au_fName FROM Inserted)

UPDATE TriggerTest SET au_name = @NewConcatName WHERE

au_id = @AuthorID

-------------------------------------

UPDATE authors SET au_fname = 'Greg'

WHERE au_id = '123-45-6789'

Trigger Examples (6)

CREATE TRIGGER tr_DeleteConcatName

ON authors FOR DELETE AS

DECLARE @AuthorID VARCHAR(11)

SELECT @AuthorID =

(SELECT au_id FROM Deleted)

DELETE FROM TriggerTest WHERE

au_id = @AuthorID

-------------------------------------

DELETE FROM authors WHERE au_lname = 'Woody'

Daftar Pustaka

http://ss64.com/sql

http://www.sqlteam.com/article/user-defined-

functions

http://databases.about.com/od/sqlserver/

Microsoft_SQL_Server.htm