Smart Database [Stored Procedures - Functions Trigger]

Transcription

1 Smart Database [Stored Procedures - Functions Trigger]

2 Stored Procedures A stored procedure is an already written SQL statement that is saved in the database. Benefits of Stored Procedures: 1. Precompiled execution 2. Reduced client/server traffic 3. Efficient reuse of code and programming abstraction 4. Enhanced security controls

3 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

4 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, procedure s 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.

5 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.

6 Stored Procedures Syntax CREATE PROC[EDURE] [schema.] procedure [ [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

7 Functions Syntax CREATE FUNCTION [schema.] function ( [@parameter [ AS ][type_schema.] parameter_data_type [= default ] [,...n ] ]) RETURNS return_clause... [;] ALTER FUNCTION DROP FUNCTION

8 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

9 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 [;] }

10 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 [;] }

11 Related Trigger Commands : ALTER TRIGGER ENABLE TRIGGER DISABLE TRIGGER DROP TRIGGER

12 Stored Procedures Samples (1) CREATE PROCEDURE [dbo].[getproducts] AS SELECT ProductID, ProductName FROM Products EXEC GetProducts

13 Stored Procedured Examples (2) CREATE PROCEDURE 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 = MAX(Quantity) FROM [Order Details] RETURN (SELECT SUM(Quantity) FROM [Order Details])

14 Stored Procedures Samples (3) INT INT = OUTPUT PRINT 'The size of the largest single order was: ' + PRINT 'The sum of the quantities ordered was: ' +

15 Stored Procedures Samples (4) CREATE PROCEDURE nvarchar(5) AS SELECT orderid,customerid,orderdate FROM Orders WHERE EXEC

16 Function Examples Scalar (1) CREATE FUNCTION whichcontinent nvarchar(15)) RETURNS varchar(30) AS BEGIN varchar(30) = 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 end

17 Function Examples - Scalar (2) PRINT dbo.whichcontinent('usa') SELECT dbo.whichcontinent(customers.country), customers.* FROM customers

18 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)

19 Function Examples - Inline Table-Valued (2) SELECT * FROM CustomersbyContinent('North America') SELECT * FROM CustomersByContinent('South America') SELECT * FROM CustomersbyContinent('Unknown')

20 Function Examples - Multi-statement Table-valued (1) CREATE FUNCTION varchar(15) ) RETURNS AS 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) )

21 Function Examples - Multi-statement Table-valued (2) INSERT SELECT [CustomerID], [CompanyName], [ContactName], [ContactTitle], [Address], [City], [PostalCode], [Country], [Phone], [Fax] FROM [Northwind].[dbo].[Customers] WHERE country

22 Function Examples - Multi-statement Table-valued (3) INT = COUNT(*) = 0 INSERT ( [CustomerID], [CompanyName], [ContactName], [ContactTitle], [Address], [City], [PostalCode], [Country], [Phone], [Fax] ) VALUES ('','No Companies Found','','','','','','','','') RETURN END

23 Function Examples - Multi-statement Table-valued (4) SELECT * FROM dbo.customersbycountry('usa') SELECT * FROM dbo.customersbycountry('canada') SELECT * FROM dbo.customersbycountry('adf')

24 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

25 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())

26 Trigger Examples (3) UPDATE dbo.products SET UnitPrice = 1 WHERE ProductID = 1 SELECT * FROM dbo.audittrail

27 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

28 Trigger Examples (4) CREATE TABLE [dbo].[triggertest] ([au_id] [int] NULL, [au_name] [varchar] (50)) CREATE TRIGGER tr_insertconcatname ON authors FOR INSERT AS VARCHAR(11) VARCHAR(50) = (SELECT au_id FROM Inserted) = (SELECT au_lname + ', ' + au_fname FROM Inserted) INSERT TriggerTest values (@AuthorID,@ConcatName) INSERT authors (au_id, au_lname, au_fname, contract) VALUES (' ', 'Woody', 'Buck', 1)

29 Trigger Examples (5) CREATE TRIGGER tr_updateconcatname ON authors FOR UPDATE AS VARCHAR(11) VARCHAR(50) = (SELECT au_id FROM Inserted) = (SELECT au_lname + ', ' + au_fname FROM Inserted) UPDATE TriggerTest SET au_name WHERE au_id UPDATE authors SET au_fname = 'Greg' WHERE au_id = ' '

30 Trigger Examples (6) CREATE TRIGGER tr_deleteconcatname ON authors FOR DELETE AS VARCHAR(11) = (SELECT au_id FROM Deleted) DELETE FROM TriggerTest WHERE au_id DELETE FROM authors WHERE au_lname = 'Woody'

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