sql server tsql [read-only] - csuohio.educis.csuohio.edu/~sschung/ist331/sql_server_tsql.pdf ·...

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SQL Server

Server Side Programming using T-SQL

Great Bison – Altamira Cave 17000 BC

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June 18, 2007 –Worldwide relational database management systems (RDBMS) total software revenue totaled $15.2 billion in 2006, a 14.2 percent increase from 2005 revenue of $13.3 billion.

Microsoft SQL Server.

Worldwide Database Market

http://www.gartner.com/it/page.jsp?id=507466Additional information is available in the Gartner report “Market Share: Relational Database Management Systems by Operating System, Worldwide, 2006.” The report is available on Gartner’s Web site at http://www.gartner.com/DisplayDocument?ref=g_search&id=507295&subref=simplesearch.

Exxon posts biggest annual profit on record for a U.S. corporation Record oil prices help the world's largest public oil company earn $39.5 billion in 2006.

CNNmoney.com http://money.cnn.com/2007/02/01/news/companies/exxon/index.htm

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Worldwide Database Market

Company 20062006

Market Share (%)

20052005

Market Share (%)

2005-2006 Growth (%)

Oracle 7,168.0 47.1 6,238.2 46.8 14.9

IBM 3,204.1 21.1 2,945.7 22.1 8.8

Microsoft 2,654.4 17.4 2,073.2 15.6 28.0

Teradata 494.2 3.2 467.6 3.5 5.7

Sybase 486.7 3.2 449.9 3.4 8.2

Other Vendors 1,206.3 7.9 1,149.0 8.6 5.0

Total 15,213.7 100.0 13,323.5 100.0 14.2

Additional information is available in the Gartner report “Market Share: Relational Database Management Systems by Operating System, Worldwide, 2006.” The report is available on Gartner’s Web site at http://www.gartner.com/DisplayDocument?ref=g_search&id=507295&subref=simplesearch.

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2006 Worldwide Database Market

Additional information is available in the Gartner report “Market Share: Relational Database Management Systems by Operating System, Worldwide, 2006.” The report is available on Gartner’s Web site at http://www.gartner.com/DisplayDocument?ref=g_search&id=507295&subref=simplesearch.

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2005 Global Database Market

Takeb from: http://www.idc.com/ Visited on 22-Oct-2006

Top Five (% market)

Oracle 44.6

IBM 21.4

Microsoft 16.8

Sybase 3.5

NCR-Teradata 2.9

Others 10.8

$14.6 Billion Dollars

May 24, 2006 – The worldwide market for relational database management systems (RDBMS) grew by 9.4% to $14.6 billion in 2005, according to preliminary figures released by IDC.

These numbers reflect steady growth for the RDBMS software market, indicating a continued increase in the deployment of relational databases.

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SQL Server 2005

Microsoft-SQL Server 2005 is a relational database management system (RDBMS) from Microsoft that's designed for the enterpriseenvironment.

SQL Server runs on T-SQL (Transact -SQL), a set of programming extensions from Sybase and Microsoft that enhances the capabilities of standard SQL.

According to Microsoft the SQL Server 2005 provides improved flexibility, scalability, reliability, and security to database applications, and makes them easier to create and deploy, it also includes more administrative support.

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Excerpts taken from (reliable ? accurate ? but always entertaining) www.wikipedia.com on Nov-2006

Sybase Inc. (NYSE: SY) is a software company specializing in relational database management systems and database-related products. "Sybase" is also commonly used to refer to Adaptive Server Enterprise, the company's flagship relational database system. Sybase's original architects were Dr. Robert Epstein and Tom Haggin who both had worked at Briton-Lee and the University of California, Berkeley Department of Computer Sciences (1984).

The pioneering "University Ingres" relational database system, developed at UC Berkeley, led to Briton-Lee, Sybase, Ingres (Computer Associates) Informix (IBM) and NonStop SQL (Tandem), as well as the majority of other SQL systems currently in use.

Sybase became the number 2 database system behind Oracle, after making a deal with Microsoft to share the source code for Microsoft to remarket on the OS/2 platform as "SQL Server". At the time, Sybase called the database server "Sybase SQL Server".


SQL Server 2005 and SYBASE

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CONT. Excerpts taken from … www.wikipedia.com on Nov-2006

Until version 4.9, Sybase and Microsoft SQL server were virtually identical. Due to disagreements between the two companies over revenue sharing (or lack thereof), Sybase and Microsoft decided to split the code-lines and went their own way, although the shared heritage is very evident in the Transact-SQL (TSQL) procedural language as well as the basic process architecture. The big difference is that Sybase has a Unix heritage, while Microsoft sprung from that original Unix architecture and was adapted and optimized only for the Microsoft Windows NT operating system. Sybase continues to offer versions for Windows, several flavors of Unix, and for Linux.

Sybase suffered a major downturn in fortune in the latter half of the 1990s when Informix started outselling it by a wide margin. Today Informix is no longer an independent company (having been bought by IBM). Today Sybase is well behind its major competitors in the enterprise database market, with 3% market share (InformationWeek March 05).

Sybase has recently returned to profitability under the management of John Chen, and continues to reinvent itself with a new 'Unwired Enterprise' strategy. The 'Unwired Enterprise' vision is about allowing companies to deliver data to mobile devices in the field as well as traditional desktops, and combines technology from Sybase's existing data management products with its new mobility products. Sybase has expanded into the mobile and wireless space through buyouts of smaller networking and wireless companies. Through its mobility subsidiary, launched in 2000, iAnywhere Solutions, Sybase has become the leader of the mobile database market with SQL Anywhere.


SQL Server 2005 and SYBASE

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SQL Server 2005 Technologies

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SQL Server Database Engine. The Database Engine is the core service for storing, processing, and securing data in either a relational (tabular) format or as XML documents.

SQL Server Analysis Services. Analysis Services delivers online analytical processing (OLAP) and data mining functionality for business intelligence applications.

SQL Server Integration Services (SSIS). Integration Services is an enterprise data transformation and data integration solution that you can use to extract, transform, and consolidate data from disparate sources and move it to single or multiple destinations.

SQL Server Replication. Replication is a set of technologies for copying and distributing data and database objects from one database to another and then synchronizing between databases to maintain consistency.

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SQL Server Reporting Services. Reporting Services is a server-based reporting platform that you can use to create and manage tabular, matrix, graphical, and free-form reports that contain data from relational and multidimensional data sources. The reports that you create can be viewed and managed over a Web-based connection.

SQL Server Notification Services. Notification Services is the platform for developing and deploying applications that generate and send notifications to thousands or millions of subscribers, and deliver them to a wide variety of devices.

SQL Server Service Broker. Service Broker also provides integration, queueing, and a message-based communication platform that can be used to link disparate application components into a functioning whole.

Full-Text Search. SQL Server contains the functionality to issue full-text queries against plain character-based data in SQL Server tables.

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SQL Server Management Studio

SQL Server Management Studio is a suite of administrative tools for managing the components belonging to SQL Server. Including

• Code Editor is a script editor for writing and editing scripts. There are four versions: the SQL Query Editor, MDX Query Editor, XML Query Editor, and SQL Mobile Query Editor.

• Object Explorer for locating, modifying, scripting or running objects belonging to instances of SQL Server.

• Template Explorer for locating and scripting templates.

• Solution Explorer for organizing and storing related scripts as parts of a project.

• Properties Window for displaying the current properties of selected objects.

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Exploring Database

1. Connect to the COMPANY database

2. Explore the contents of selected database

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Table Structure

1. Select a table.

2. Right-click.

3. Select MODIFY option to see/change structure of a table.

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Multiple Databases

1. Select another database and explore a table.

2. Right-click on NorthwindSQL.

3. Open the Product table

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Creating 0bjects (using a script)

1. Select the COMPANY database and create a new table

2. Click on “New Query”

3. Type code (screen)

4. Hit F5 to execute batch

5. You may also use the GUI interface to “Add New Table”

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Mixing Databases / Temporary Tables

1. Double dot to reach other SQL database table. For example NorthWindSQL..Products

2. Prefix with # a table name to create a temporary table. For example #MyData

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Temporary Tables

Prefix with # a table name to

create a temporary table. For

example #EmpCopy

Notation N’myTable’ indicates

Unicode string (not needed for Germanic – Romance languages)

Examples:

select * into #EmpCopy from employee

create table #Auditing (Clock DateTime, Msg nvarchar1(100) )

Related Topics

Drop Table myTable

If exists (select * from sysObjects where name= N’myTable’)drop table myTable

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Database Diagram

exposing Referential-Integrity

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-- useful system functionsselect user, current_timestamp, @@servername, @@version

dbo

2006-10-22 14:57:02.233

CARIBE

Microsoft SQL Server 2005 - 9.00.1399.06 (Intel X86) Oct 14 2005 00:33:37 Copyright (c) 1988-2005 Microsoft Corporation Standard Edition on Windows NT 5.1 (Build 2600: Service Pack 2)


Useful Functions

use Company

select db_name()

Company

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What is T-SQL ?

T-SQLTransac-SQL

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What is T-SQL ?

T-SQL (Transact-SQL) is a set of programming extensions from Sybase and Microsoft that adds procedural features to the Structured Query Language (SQL) including

• sequential logic, • structured programming, • transaction control, • conditional logic, • iteration, • recursion,• exception and error handling, • row processing, and • declared variables.

Microsoft's SQL Server and Sybase's SQL server support T-SQL statements.

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T-SQL Language Elements

Transact-SQL element Description

• Identifiers. Names of objects such as tables, views, columns, databases, and servers.• Data Types. Define the types of data that are contained by data objects, such as columns, variables, and parameters. • Functions. Routines that take zero or one or more input values and return a scalar value or a tabular set of values. • Expressions. Units of syntax that SQL Server can resolve to single values. • Operators in Expressions. Work with one or more simple expressions to form a more complex expression. • Comments. Pieces of text included to explain the purpose of the statement. • Reserved Keywords. Words that are reserved for use by SQL Server and should not be used for the names of objects in a database.

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Regular identifiers

Salary @Salary Salary123 Boss_Salary

Delimited identifiers Are enclosed in double quotation marks (") or brackets ([ ]).

[Big Salary] “StrangeName” [First Name]

Rules for Regular Identifiers1. The first character must be one of the following:

• A letter • The underscore (_), "at" sign (@), or number sign (#). • #Name denotes a temporary table or procedure. • ##Name denotes a global temporary object. • @@Name usually denotes TSQL global functions

2. Other valid symbols are: Letters, digits, @, $, _ (up to 128 char.)


T-SQL IDENTIFIERS

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Regular identifiers

Salary @Salary Salary123 Boss_Salary

Delimited identifiers Are enclosed in double quotation marks (") or brackets ([ ]).

[Big Salary] “StrangeName” [First Name]

Examples

declare @var1 intdeclare @var2 numeric(10,2), @var3 nvarchar(20)


T-SQL IDENTIFIERS

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Data Types

Exact

Numerics

Approximate

Numerics

Character

Strings

Unicode

Character Strings

Binary

Strings

Other

Data Types

bigint

decimal

int

numeric

smallint

money

tinyint

smallmoney

bit

float

real

char

text

varchar

nchar

ntext

nvarchar

binary

image

varbinary

cursor

timestamp

sql_variant

uniqueidentifier

table

xml

Datetime

smallDateTime

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Function category Description

Aggregate Functions (Transact-SQL) Summary operations. Examples are COUNT, SUM, MIN, and MAX.

Configuration functions Scalar functions that return information about configuration settings.

Cryptographic Functions (Transact-SQL) Support encryption, decryption, digital signing, and the validation of digital signatures.

Cursor functions Return information about the status of a cursor.

Date and Time functions Change date and time values.

Mathematical functions Perform trigonometric, geometric, and other numeric operations.

Metadata functions Return information about the attributes of databases and database objects.

Ranking functions Nondeterministic functions that return a ranking value for each row in a partition.

Rowset Functions (Transact-SQL)Return the rowsets that can be used in the place of a table reference in a Transact-SQL statement.

Security functions Return information about users and roles.

String functions Change char, varchar, nchar, nvarchar, binary, and varbinary values.

System functions Operate on or report on various system level options and objects.

System Statistical Functions (Transact-SQL) Return information about the performance of SQL Server.

Text and image functions Change text and image values.


SQL-Server Functions

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Aggregation Configuration Cursor Strings

AVG

MIN

CHECKSUM

SUM

CHECKSUM_AGG

STDEV

COUNT

STDEVP

COUNT_BIG

VAR

GROUPING

VARP

MAX

@@DATEFIRST

@@OPTIONS

@@DBTS

@@REMSERVER

@@LANGID

@SERVERNAME

@@LANGUAGE

@@SERVICENAME

@@LOCK_TIMEOUT

@@SPID

@@MAX_CONNECTIONS

@@TEXTSIZE

@@MAX_PRECISION

@@VERSION

@@NESTLEVEL

@@CURSOR_ROWS

@@FETCH_STATUS

CURSOR_STATUS

ASCII

CHAR

CHARINDEX

DIFFERENCE

LEFT

LEN

LOWER

LTRIM

NCHAR

PATINDEX

QUOTENAME

REPLACE

REPLICATE

REVERSE

RIGHT

RTRIM

SOUNDEX

SPACE

STR

STUFF

SUBSTRING

UNICODE

UPPER

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Date & Time

Mathematical MetaData

DATEADD

DATEDIFF

DATENAME

DATEPART

DAY

GETDATE

GETUTCDATE

MONTH

YEAR

ABS

ACOS

ASIN

ATAN

ATN2

CEILING

COS

COT

DEGREES

EXP

FLOOR

LOG

LOG10

PI

POWER

RADIANS

RAND

ROUND

SIGN

SIN

SQRT

SQUARE

TAN

@@PROCID

COL_LENGTH

COL_NAME

COLUMNPROPERTY

DATABASEPROPERTY

DATABASEPROPERTYEX

DB_ID

DB_NAME

FILE_ID

FILE_IDEX (Transact-SQL)

FILE_NAME

FILEGROUP_ID

FILEGROUP_NAME

FILEGROUPPROPERTY

FILEPROPERTY

FULLTEXTCATALOGPROPERTY

FULLTEXTSERVICEPROPERTY

INDEX_COL

INDEXKEY_PROPERTY

INDEXPROPERTY

OBJECT_ID

OBJECT_NAME

OBJECTPROPERTY

OBJECTPROPERTYEX

SQL_VARIANT_PROPERTY

TYPE_ID

TYPE_NAME

TYPEPROPERTY

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Using batches A batch is a group of one or more Transact-SQL statements that are sent from an application to the server as one unit.

Using stored procedures A stored procedure is a group of Transact-SQL statements that have been predefined and precompiled on the server. They can accept parameters, and return result sets, return codes, and output parameters to the caller.

Using triggers A trigger is a special type of stored procedure. It is not called directly by applications. It is instead executed whenever a user performs a specified modification (INSERT, UPDATE, or DELETE) to a table.

Using scripts A script is a series of Transact-SQL statements stored in a file. The file can be used as input to the sqlcmd utility or SQL Server Management Studio Code editor.


Procedural T-SQL

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Flow-Control, Iteration Statements

BEGIN...END

BREAK

CONTINUE

GOTO

IF...ELSE

RETURN

WAITFOR

WHILE

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Var Declaration – Assignment Statement

-- assignment operator (SELECT or SET)

declare @var1 int

declare @var2 numeric(10,2), @var3 nvarchar(20)

set @var1= 123

select @var1 = 123 -- same as previous assignment

set @var2 = 19.99

set @var3 = 'Juan Valdez'

set @var2 = CAST(@var1 as numeric(10,2) )

set @var2 = CONVERT(numeric, @var1)

set @var3 = 'Room No. ' + Str(@var1)

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Flow-Control Statements

BEGIN

statement-1

statement-2

…

statement-n

END

IF @Grade >= 75

print ‘Pass’

ELSE

print ‘Fail’

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Flow-Control Statements

declare @n int

set @n = 5

WHILE @n > 0

BEGIN

print 'n= ' + str(@n)

set @n = @n - 1

END

declare @n int

select * from employee

set @n = @@rowCount

IF @n = 0

print 'No data found'

ELSE

print 'Total rows: ' + str(@n)

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The following example uses the DELAY keyword to wait for two seconds before performing a SELECT statement:

WAITFOR DELAY '00:00:02'SELECT * FROM Employee;

The following example uses the TIME keyword to wait until 10 P.M. to perform a check of the Company database to make sure that all Projects are in progress

USE Company;GOBEGIN

WAITFOR TIME '22:00:00';exec CloseTheGates

END;GO


WAITFOR Flow-Control Statements

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Binding Local Variables with SQL statements

BEGIN

declare @id int

declare @sal money

declare @name nvarchar(20)

select @id = ssn, @sal = salary, @name=fname

from employee

where lname like 'Smith%'

print str(@id) + ' ' + str(@sal) + ' ' + @name

END

Go

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Binding Local Variables with SQL statements

declare @OldSalary money

update employee

set @OldSalary = salary,

salary = salary + 1

where ssn=123456789

print 'Old salary: ' + str(@OldSalary)

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Using the global @@ERROR variable

BEGIN

update employee

set salary = salary / 0

where ssn= 123456789

if @@error <> 0

print 'Some bizarre problem ' +

'happened here! - ' +

'call Xagents Mulder & Scully'

END

Msg 8134, Level 16, State 1, Line 2Divide by zero error encountered.The statement has been terminated.Some bizarre problem happend here! - call Mulder and Scully

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Using the global @@ROWCOUNT variable

Delete employees working for dno 4 (then restore the table)-- create temporary copy of the EMPLOYEE table

select * into #EmpCopy from employee

go

declare @myCount int

BEGIN

begin transaction

delete from #EmpCopy where dno = 4

-- @@rowCount tells how many rows were affected in previous stm.

set @myCount = @@rowCount

if @myCount > 0 begin

select * from #EmpCopy

print 'Deleted rec.= ' + str(@myCount)

rollback

print 'employee table restored'

end

else begin

print 'NO rec. deleted ' + str(@myCount)

commit

end

END

select * from #EmpCopy

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Using the global @@ROWCOUNT variable

Transaction Processing

Begin Transaction

statement

statement

…

statement

Commit (or Rollback)

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Using the RAND() Function

delete from mylog

declare @msg varchar(50), @num int, @n int

set @n = 5

while @n > 0

begin

--make a random numb between 1..100

set @num = RAND() * 100 + 1

set @msg = 'Random message number ' + str(@num)

insert into mylog values (@n, @msg)

set @n = @n - 1

end

select * from mylog

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T-SQL Cursors

T-SQL Cursors

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T-SQL Cursors

A SQL select-statement retrieves a complete set of rows. Some applications may need a mechanism to work with one row or a small block of rows at a time.

Cursors are an extension to result sets that provide that mechanism by

• Allowing positioning at specific rows of the result set.

• Retrieving one row or block of rows from the current position in the result set.

• Supporting data modifications to the rows at the current position in the result set.

• Supporting different levels of visibility to changes made by other users to the database data that is presented in the result set.

• Providing Transact-SQL statements in scripts, stored procedures, and triggers access to the data in a result set.

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T-SQL Cursors

Syntax

-- drop an existing cursor

deallocate curPeople

-- create a cursor

declare curPeople cursor for

select fname, salary

from employee

where dno = 4

-- open / close cursor

open curPeople

close curPeople

-- fetching rows / checking state

fetch from curPeople into @var1, @var2, ....

@@fetch_status ( 0 when data read )

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T-SQL Cursors

EXAMPLE-- get first & last name of female employees



select fname, lname

from employee

where sex = 'F'

--define local variables to store from cursor

declare @fn nvarchar(20), @ln varchar(20)

open curPeople

fetch from curPeople into @fn, @ln

while(@@fetch_status = 0)

begin

print @fn + ' ' + @ln

fetch from curPeople into @fn, @ln

end

close curPeople

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Go


select fname, salary

from employee

Go

BEGIN TRANSACTION

declare @eName nvarchar(100), @eSal numeric(10,2)

open curPeople

fetch from curPeople into @eName, @eSal

while @@fetch_status = 0 begin

if @eSal < 40000 begin

update employee set salary = salary + 1

where current of curPeople

print 'New salary >>> ' + @eName + str(@eSal)

end

fetch from curPeople into @eName, @eSal

end

close curPeople

ROLLBACK TRANSACTION

Go


T-SQL Forward-Only Cursors

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--scrollable cursors

deallocate scrPeople

declare scrPeople scroll cursor for

select (fname + N' ' + lname) as fullName, salary from employee order by salary

declare @eName nvarchar(100), @eSal numeric(10,2)

open scrPeople

fetch NEXT from scrPeople into @eName, @eSal

print str(@@fetch_status) + ' ' + @eName + char(9) + str(@eSal)

fetch LAST from scrPeople into @eName, @eSal


fetch PRIOR from scrPeople into @eName, @eSal


-- Fetch the second row in the cursor

fetch ABSOLUTE 2 from scrPeople into @eName, @eSal


-- Fetch the row that is 10 rows after the current row

fetch RELATIVE + 10 from scrPeople into @eName, @eSal


close scrPeople


T-SQL Scrollable - Cursors

0 Joyce English 302510 James Borg 606370 Jennifer Wallace 474070 Ahmad Jabbar 30251-1 Ahmad Jabbar 30251

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T-SQL Stored Procedures

T-SQL Stored Procedures

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T-SQL Stored Procedures with OUTPUT values

IF EXISTS (select * from SYSOBJECTS where name = 'GetDepartment')

DROP PROCEDURE GetDepartment

GO

create procedure GetDepartment (@ID int, @depName nvarchar(20) output)as

BEGIN

select @depName = d.dname from employee e, department d

where e.dno = d.dnumber and e.ssn = @ID

if @@rowCount = 1

return 0 -- department found

else begin

set @depName = ''

return 1 -- department NOT found

end

END

GO

declare @answer nvarchar(20)

Set @answer = '***'

exec GetDepartment 123456789, @answer output

print 'The Department for 123456789 is: ' + @answer

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set @answer = ''

exec GetDepartment 123456789, @answer output


GO

The Department for 123456789 is: Research

declare @myRetCode int


set @answer = '***'

set @myRetCode = -1

Execute @myRetCode = GetDepartment 123456789, @answer OUTPUT

print 'The ReturnCode is ' + Str(@myRetCode)


GO

The ReturnCode is 0

The Department for 123456789 is: Research

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Private Function UseSsnToGetDeptName(ByVal aSSN As Integer) As String

Dim myCnn As New SqlConnectionDim myCmd As New SqlCommand

myCnn.ConnectionString = "Data Source=Localhost;Initial Catalog=Company;Integrated Security=True"myCnn.Open()

myCmd.CommandType = CommandType.StoredProceduremyCmd.Connection = myCnnmyCmd.CommandText = "GetDepartment"

myCmd.Parameters.Clear()myCmd.Parameters.Add("@empSSN", SqlDbType.Int)myCmd.Parameters.Add("@depName", SqlDbType.VarChar, 100)myCmd.Parameters("@depName").Direction = ParameterDirection.Output

myCmd.Parameters("@empSSN").Value = aSSNmyCmd.Parameters("@depName").Value = "***"

myCmd.ExecuteNonQuery()

Return (myCmd.Parameters("@depName").Value)myCnn.Close()

End Function

Microsoft SQL Server. Using a .NET program to reach a


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-- STORED PROCEDURES: returned values (OUTPUT vars), DEFAULT values

drop procedure pr_GetSalaryGo

create proc pr_GetSalary( @id int,

@sal numeric(20,2) output,@currency nvarchar(10) = 'usd' )

as

declare @ctr int, @xrate numeric(10,2)

BEGIN

set @sal = 0

select @sal = salary from employee where ssn = @id

if @@rowCount = 0 return -1

if @currency = 'usd' set @xrate = 1.00

if @currency = 'euros' set @xrate = 0.73

if @currency = 'bolivares' set @xrate = 2700.00

select @sal = salary from employee where ssn = @id

set @sal = @sal * @xrate

return 0

END

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--Testing OUTPUT proc and RETURN values

declare @result numeric(20,2), @retCode int

set @result = 0, ret

--no currency supplied (use default 'usd' )

exec pr_GetSalary 987654321, @result output

print 'Salary (usd) = ' + str(@result)

exec pr_GetSalary 987654321, @result output, 'euros'

print 'Salary (euros) = ' + str(@result)

exec pr_GetSalary 987654321, @result output, 'bolivares'

print 'Salary (bolivares) = ' + str(@result)

-- using RETURN CODES. No currency supplied (use default 'usd' )

exec @retCode = pr_GetSalary 123, @result output

print 'Return code is: ' + str(@retCode) + ' Salary (usd) = ' + str(@result)

exec @retCode = pr_GetSalary 123456789, @result output

print 'Return code is: ' + str(@retCode) + ' Salary (usd) = ' + str(@result)

go

Salary (usd) = 47407Salary (euros) = 36977Salary (bolivares) = 118517500

Return code is: -1 Salary (usd) = 0

Return code is: 0 Salary (usd) = 36314

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T-SQL Stored Functions

drop function dbo.fnGetName

go

CREATE FUNCTION dbo.fnGetName (@aSSN int)RETURNS nvarchar(80)AS BEGIN

-- Returns salutation + full-name of given employeeDECLARE @answer nvarchar(100), @gender nvarchar(2)

set @answer = ''

select @gender = sex from employee where ssn = @aSSN;

if @@rowcount = 0 RETURN @answer;

select @answer = (fname + ' ' + lname) from employee

where ssn = @aSSN;

if @gender = 'F'

set @answer = 'Ms. ' + @answer

else

set @answer = 'Mr. ' + @answer;

RETURN @answer

END;

GO

declare @person nvarchar(100)

set @person = dbo.fnGetName (123456789)print @person

select ssn, dbo.fnGetName(ssn) from employee

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Imports Microsoft.SqlServer.Server

Imports System.Data.SqlClient

Public Class T

<SqlFunction(DataAccess:=DataAccessKind.Read)> _

Public Shared Function GetFullName(ByVal aSSN As Integer) As Integer

Using conn As New SqlConnection("context connection=true")

conn.Open()

Dim mySQL As String = "SELECT (Fname + ' ' + Lname) as FullName, sex " & _

" FROM Employee WHERE ssn = " & aSSN

Dim cmd As New SqlCommand(mySQL, conn)

Dim DR As SqlDataReader

Dim answer As String = "* * *"

DR = cmd.ExecuteReader()

If DR.Read Then

If DR("sex") = "F" Then

answer = "Ms. " + DR("fullName")

Else

answer = "Mr. " + DR("FullName")

End If

End If

Return answer

End Using

End Function

End Class


CLR Stored Functions

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drop assembly myFunction

go

CREATE ASSEMBLY myFunction FROM 'c:\temp\SQLCLRfunction.dll'

go

CREATE FUNCTION GetName() RETURNS nvarchar

AS EXTERNAL NAME SQLCLRfunction.T.GetName

go

declare @X nvarchar(100)

SET @x = dbo.GetName()

go


CLR Stored Functions

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T-SQL Exceptions & RAISERROR command

Error Handling

61



The command: raiserror behaves like C printf(…)

raiserror(text-message, severity, state, arguments)

Parameters:text-messageseverity(0-18), state(0-127), arguments (used in combination with % formatters)

Example:raiserror('Error. negative argument %d',17, 55, @arg1)

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-- EXCEPTIONS. Using RAISERROR command

drop procedure TestError

Go

create procedure TestError (@arg1 int)

as

begin

if @arg1 < 0 begin

--raisError behaves like C printf(…)

--severity(0-18), state(0-127), arguments

raiserror('Error. negative argument %d',17, 55, @arg1)

end

print 'Busy doing something here with ' + str(@arg1)

print 'Adios from your friendly procedure'

end

Go

exec TestError -11

Busy doing something here with -11Adios from your friendly procedureMsg 50000, Level 17, State 55, Procedure TestError, Line 6Error. negative argument -11

Warning: Exception is RAISED but execution continues !

63


T-SQL Exceptions & RAISERROR command-- EXCEPTIONS. Using RAISERROR command

drop procedure pr_Spouse

Go

create procedure pr_Spouse (@id int, @spouseName nvarchar(20) output)

as

BEGIN

set @spouseName = '***'select * from employee where ssn = @id

if @@rowCount=0 begin

--message like C printf, severity(0-18), state(0-127), arguments

raiserror('Error1. Invalid employee SSN %d',17, 55, @id)

-- raiserror('Error2. Invalid employee SSN %d',17, 55, @id)

-- raiserror('Error3. Invalid employee SSN %d',17, 55, @id)

-- return 1

end

select @spouseName = dependent_name

from dependent

where relationship = 'Spouse' and essn = @id

if @@rowCount=0

return 2

else

return 0

END

go

declare @mate nvarchar(40), @retCode int

execute @retCode = pr_Spouse 123, @mate output

print 'Spouse: ' + @mate + ' - Return Code: ' + ltrim(str(@retCode))

(0 row(s) affected)Spouse: *** Return Code: 1Msg 50000, Level 17, State 55, Procedure pr_Spouse, Line 9Error. Invalid employee SSN 123

64

Imports System.Data.SqlClient

Public Class Form1

Private Sub btnFind_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

Handles btnFind.Click

Try

Dim myCnn As New SqlConnection

Dim myCmd As New SqlCommand

myCnn.ConnectionString = "Data Source=Localhost;Initial Catalog=CompanySQL;

Integrated Security=True"

myCnn.Open()

myCmd.CommandType = CommandType.StoredProcedure

myCmd.CommandText = "pr_Spouse"

myCmd.Connection = myCnn

myCmd.Parameters.Clear()

myCmd.Parameters.Add("@id", SqlDbType.BigInt)

myCmd.Parameters.Add("@spouseName", SqlDbType.VarChar, 20)

myCmd.Parameters("@spouseName").Direction = ParameterDirection.Output

myCmd.Parameters("@id").Value = Me.txtSSN.Text

myCmd.Parameters("@spouseName").Value = "***"

Dim myReturnCode As Integer

myReturnCode = myCmd.ExecuteNonQuery

Me.txtSpouse.Text = myCmd.Parameters("@spouseName").Value

myCnn.Close()

Catch ex As Exception

MsgBox(ex.Message)

End Try

End Sub

End Class



65


T-SQL Transactions

Transaction Processing

66


T-SQL Transactions

What is a transaction?

A transaction is a group of statements treated as a monolithic block that must either succeed or fail in its integrity.

Example --Transfer $1M from saving to checking account

Problem. If the first statement succeeds but the second statement fails the customer looses $1M

BEGINExecute Procedure to Withdraw $1M from SavingAccount XYZ_SAVExecute Procedure to Deposit $1M into CheckingAccount XYZ_CHK

END

67


T-SQL Transactions

Solution--Transfer $1M from saving to checking account as a Transaction

BEGIN TRANSACTION

Execute Procedure to Withdraw $1M from SavingAccount XYZSAVExecute Procedure to Deposit $1M into CheckingAccount XYZCHK

COMMIT TRANSACTION

• The two operations are treated as a single (indivisible/atomic) statement.

• The two of them MUST satisfactorily execute or both of them will be rolled-back and the changes they made will be UNDONE.

68


T-SQL Transactions

Transaction Control Statements

Begin Transaction Marks the beginning of a critical region.

Commit Transaction Make changes be permanent.

Rollback Transaction Undo all changes up to begin tran or save-point.

Save Transaction <Label> Marks a save-point for partial rollbacks

69


Transaction Control Statements

Transaction Control Statement Effect on @@tranCount

Begin Tran

Commit Tran

Rollback [Tran]

RollBack [Tran <savepoint name>]

Save Tran [<savepoint name>]

+1

-1

Reset to 0

None

none

70


T-SQL Transactions

Example

declare @myCount int

--STEP1. How many Projects are there?select @myCount = count(*) from project

print 'Num. Projects= ' + str(@myCount)

BEGIN TRANSACTION

--STEP2. Add a new Projectinsert into Project values ('Bogus Project',0, 'NY',1)

select @myCount = count(*) from project



--STEP1. How many Projects are there?select @myCount = count(*) from project


Num. Projects= 6

(1 row(s) affected)Num. Projects= 7

Num. Projects= 6

71


T-SQL Transactions

EXAMPLE. Transfer $1M from saving to checking accountdrop table #BankAccount

create table #BankAccount ( No integer, Type nvarchar(10), Balance money)

insert into #BankAccount values (111, 'Saving', 900000)

insert into #BankAccount values (111, 'Checking', 20)

insert into #BankAccount values (222, 'Checking', 100)

go

select * from #BankAccount

go

Begin transaction

declare @savingBalance money

--subtract $1M from saving account

update #BankAccount set balance = balance - 1000000 where No= 111 and Type = 'Saving'

select @savingBalance = balance from #BankAccount where No= 111 and Type = 'Saving'

--deposit $1M into checking account

update #BankAccount set balance = balance - 1000000 where No= 111 and Type = 'Checking'

--finish the transfer operation

if @savingBalance >= 0 begin

print 'Successful transfer operation'

commit tran

end

else begin

print 'Problem. Insufficient (saving) funds '

rollback tran

end

print 'Thanks for using our bank'

select * from #BankAccount

Problem. Insufficient (saving) funds Thanks for using our bank

72


T-SQL Transactions

Implicit TransactionsThe commands listed in the table below are executed in isolation as a complete and self-contained transaction.

<begin tran>Database_command

<commit tran>

ALTER TABLE FETCH REVOKE

CREATE GRANT SELECT

DELETE INSERT TRUNCATE TABLE

DROP OPEN UPDATE

To change this behavior use the command

SET IMPLICIT_TRANSACTIONS { ON | OFF }

73


T-SQL Transactions

Error Checking in Transactions

The global variable @@error returns the error number for the last Transact-SQL statement executed.

begin tran

update employee set salary = salary / 0

if @@error <> 0 begin

print 'Problems – but ready to roll'

rollback tran

end

print 'Last Line'

Msg 8134, Level 16, State 1, Line 3Divide by zero error encountered.The statement has been terminated.Problems – but ready to rollLast Line

74


T-SQL Transactions

USING SAVEPOINTSdrop table #temp

select * into #Temp from works_on where essn = -1

Go

begin tran

save tran Step1

insert into #temp values(1,1,1)

save tran Step2


save tran Step3


rollback tran

select * from #temp

begin tran

save tran Step1


save tran Step2


save tran Step3


rollback tran Step2

select * from #temp

75



-- EXCEPTIONS. Using RAISERROR command

declare @person nvarchar(20), @code int

set @code = 0

exec @code = pr_Spouse 666884444, @person output

print 'Spouse name: ' + @person + ' Ret code: ' + str(@code)





Spouse name: Ret code: 2Spouse name: Abner Ret code: 0Spouse name: Ret code: 2

Msg 50000, Level 17, State 55, Procedure pr_Spouse, Line 8Error. Invalid SSN 123

76


T-SQL Recursion

drop procedure recurFactorial

go

create procedure RecurFactorial (@n int, @result int output)

as

BEGIN

declare @nminus1 int

print 'n ' + str(@n) + ' result: ' + str(@result)

if @n = 1 begin

set @result = 1

return

end

set @nminus1 = @n - 1

exec RecurFactorial @nminus1, @result output

set @result = @n * @result

print 'n ' + str(@n) + ' result: ' + str(@result)

return

END

go

declare @arg int; set @arg = 0

exec RecurFactorial 4, @arg output

print 'Arg: ' + str(@arg)

n 4 result: 0n 3 result: 0n 2 result: 0n 1 result: 0n 1 result: 2n 2 result: 6n 3 result: 24Arg: 24

77


T-SQL TRIGGERS

T-SQL Triggers

78


T-SQL TRIGGERS

Insert into works_on(Essn,Pno, Hours) values (123456789, 10, 40);

WORKS_ON table

ESSN PNO HOURS

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

123456789 1 32.5

123456789 2 7.5

666884444 3 40

453453453 1 20

453453453 2 20

333445555 2 10

333445555 3 10

333445555 10 10

333445555 20 10

999887777 30 30

999887777 10 10

987987987 10 35

987987987 30 5

987654321 30 20

987654321 20 15

888665555 20 0

TRIGGER T008BON WORKS_ON AFTER UPDATE

AS BEGIN. . . END

TRIGGER Trg_NoOverload ON WORKS_ON AFTER INSERT

AS BEGIN--Employees can not work more than 40 hours/week. . .. . .END;

Msg 3609, Level 16, State 1, Line 2The transaction ended in the trigger. The batch has been aborted.

Msg 50000, Level 17, State 55, Procedure Trg_NoOverload, Line 23

Violation to rule: max 40 hrs/week 123456789

79


T-SQL TRIGGERS

Microsoft SQL Server 2005 provides two primary mechanisms for enforcing business rules and data integrity• constraints and • triggers.

A trigger is a special type of stored procedure that automatically takes effect when a language event executes. SQL Server includes two general types of triggers: • DML triggers and • DDL triggers.

SQL Server allows for creating multiple triggers for any specific statement.

Note: Constrains include clauses such as: Primary and Foreign Keys, Nulls, Duplicates, Check, etc.

80


T-SQL TRIGGERS

CREATE TABLE table_name

( { < column_definition > | < table_constraint > } [ ,...n ] )

< column_definition > ::=

{ column_name data_type } [ { DEFAULT constant_expression

| [ IDENTITY [ ( seed , increment ) ] ] } ]

[ ROWGUIDCOL ]

[ < column_constraint > [ ...n ] ]

< column_constraint > ::= [ CONSTRAINT constraint_name ]

{ [ NULL | NOT NULL ]

| [ PRIMARY KEY | UNIQUE ]

| REFERENCES ref_table [ ( ref_column ) ]

[ ON DELETE { CASCADE | NO ACTION } ]

[ ON UPDATE { CASCADE | NO ACTION } ]

}

< table_constraint > ::= [ CONSTRAINT constraint_name ]

{ [ { PRIMARY KEY | UNIQUE }

{ ( column [ ,...n ] ) }

]

| FOREIGN KEY

( column [ ,...n ] )

REFERENCES ref_table [ ( ref_column [ ,...n ]

) ]

[ ON DELETE { CASCADE | NO ACTION } ]

[ ON UPDATE { CASCADE | NO ACTION } ]

}

Basic Referential Integrity & Column Constraints

Triggers extend this type of simpleconstraints

81


T-SQL TRIGGERS

DDL triggers are invoked when a data definition language (DDL) event takes place in the server or database (CREATE, DROP, ALTER,…).

DML triggers are invoked when a data manipulation language (DML) event takes place in the database.

1. DML events include INSERT, UPDATE, or DELETE statements that modify data in a specified table or view.

2. A DML trigger can query other tables and can include complex Transact-SQL statements.

3. The trigger and the statement that fires it are treated as a single transaction, which can be rolled back from within the trigger.

4. If a severe error is detected (for example, insufficient disk space), the entire transaction automatically rolls back.

82


T-SQL TRIGGERS

DML triggers are useful in these ways:

1. They can cascade changes through related tables in the database.

2. They can guard against malicious or incorrect INSERT, UPDATE, and DELETE operations and enforce other restrictions that are more complex than those defined with CHECK constraints.

3. Unlike CHECK constraints, DML triggers can reference columns in other tables.

4. They can evaluate the state of a table before and after a data modification and take actions based on that difference.

5. Multiple DML triggers of the same type (INSERT, UPDATE, or DELETE) on a table allow multiple, different actions to take place in response to the same modification statement.

83


T-SQL TRIGGERS

Kinds of DML Triggers

AFTER TriggersAFTER triggers are executed after the action of the INSERT, UPDATE, or

DELETE statement is performed (same as FOR used in earlier versions of Microsoft SQL Server). AFTER triggers can be specified only on tables.

INSTEAD OF TriggersINSTEAD OF triggers are executed in place of the usual triggering action.

They can also be defined on views with one or more base tables, where they can extend the types of updates a view can support.

CLR Triggers (Common Language Runtime)

A CLR Trigger can be either an AFTER or INSTEAD OF trigger. A CLR trigger can also be a DDL trigger. Instead of executing a Transact-SQL stored procedure, a CLR trigger executes one or more methods written in managed code that are members of an assembly created in the .NET Framework and uploaded in SQL Server.

84


T-SQL TRIGGERS

Function AFTER trigger INSTEAD OF trigger

Applicability Tables Tables and views

Quantity per table or view Multiple per triggering action (UPDATE, DELETE, and INSERT)

One per triggering action (UPDATE, DELETE, and INSERT)

Cascading references No restrictions apply INSTEAD OF UPDATE and DELETE triggers are not allowed on tables that are targets of cascaded referential integrity constraints.

Execution After:

1. Constraint processing

2. Declarative referential actions

3. inserted and deleted tables creation

4. The triggering action

Before: Constraint processing

In place of: The triggering action

After: inserted and deleted tables creation

Order of execution First and last execution may be specified Not applicable

varchar(max), nvarchar(max), and varbinary(max) column references in inserted and deleted tables

Allowed Allowed

text, ntext, and image column references in inserted and deleted tables

Not allowed Allowed

85

DML TRIGGER SYNTAXTrigger on an INSERT, UPDATE, or DELETE statement to a table or view

CREATE TRIGGER [ schema_name . ]trigger_name

ON { table | view }

[ WITH <dml_trigger_option> [ ,...n ] ]

{ FOR | AFTER | INSTEAD OF }

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

[ WITH APPEND ]

[ NOT FOR REPLICATION ]

AS { sql_statement [ ; ] [ ...n ] | EXTERNAL NAME <method

specifier [ ; ] > }

<dml_trigger_option> ::=

[ ENCRYPTION ]

[ EXECUTE AS Clause ]

<method_specifier> ::=

assembly_name.class_name.method_name


T-SQL TRIGGERS

86


T-SQL TRIGGERS

Example. No employee should work on more than 4 assignments

CREATE TRIGGER Trg_MaxFourJobs

ON Works_On AFTER INSERT

AS BEGIN

-- no employee should work on more than four projects

if exists(select * from works_on

group by essn having count(*) > 4)

begin

raiserror('Error. More than 4 assignments', 17,55)

rollback tran

end

END

GO

87


T-SQL TRIGGERS

Example. No employee should work on more than 4 assignments (cont.)

-- testing the trigger

select essn, count(*)as jobs

from works_on group by essn

insert into works_on

values (333445555,1,1)

Go

select essn, count(*)as jobs

from works_on group by essn

Go

Msg 3609, Level 16, State 1, Line 2The transaction ended in the trigger. The batch has been aborted.

Msg 50000, Level 17, State 55, Procedure Trg_MaxFourJobs, Line 8Volation. More than four assignments

88


T-SQL TRIGGERS

DELETED and INSERTED tables

The SQL-Server provides two memory-resident tables called INSERTEDand DELETED to test the effects of certain data modifications and to set conditions for DML trigger actions.

You cannot directly modify the data in the tables or perform data definition language (DDL) operations on the tables, such as CREATE INDEX.

In DML triggers, the inserted and deleted tables are primarily used to perform the following:

1. Extend referential integrity between tables.2. Insert or update data in base tables underlying a view.3. Test for errors and take action based on the error.4. Find the difference between the state of a table before and after a

data modification and take actions based on that difference.

89


T-SQL TRIGGERS


The deleted table stores copies of the affected old rows during DELETEand UPDATE statements.

During the execution of a DELETE or UPDATE statement, old rows are deleted from the trigger table and transferred to the deleted table.

The inserted table stores copies of the affected new rows during INSERTand UPDATE statements.

During an insert or update transaction, new rows are added at the same time to both the inserted table and the trigger table. The new rows in the inserted table are copies of the new rows in the trigger table.

90


T-SQL TRIGGERS


An update transaction is similar to a delete operation followed by an insertoperation; the old rows are copied to the deleted table first, and then the new rows are copied to the trigger table and to the inserted table.

Table \ Operation insert delete update

INSERTED Yes Empty Yes

DELETED Empty Yes Yes

91


T-SQL TRIGGERS

Example1A. Spying on the INSERTED and DELETED tables

CREATE TRIGGER Trg_SpyInsertedDeleted

ON Project AFTER UPDATE

AS BEGIN

-- spying on the DELETED and UPDATED tables

select * from inserted

select * from deleted

select * from Project

END

GO

update Project set Pname = upper(Pname) where Dnum = 4

92


T-SQL TRIGGERS

Example1A. Spying on the INSERTED and DELETED tables

INSERTED(new images)

DELETED(old images)

Updated version of the PROJECT table

93


T-SQL TRIGGERS

Example1B. Spying on the INSERTED and DELETED tables

DROP TRIGGER Trg_SpyInsertedDeleted

GO

CREATE TRIGGER Trg_SpyInsertedDeleted

ON Project AFTER UPDATE

AS BEGIN


select 'Inserted', * from inserted

select 'Deleted', * from deleted

select 'Modified', * from Project

END

GO

BEGIN TRANSACTION

select 'Before update', * from Project

update Project set Pname = upper(Pname) where Dnum = 4

select 'After update', * from Project


GO

select 'After Rollback', * from Project

Go

94


T-SQL TRIGGERS

Example1B1. Spying on the INSERTED and DELETED tables

95


T-SQL TRIGGERS


96


T-SQL TRIGGERS


97


T-SQL TRIGGERS

Example2. Spying on the INSERTED and DELETED tables CREATE TRIGGER Trg_SpyInsertedDeleted2

ON ProjectCopy AFTER DELETE

AS BEGIN

-- spying on DELETED and UPDATED

select 'inserted', * from inserted

select 'deleted', * from deleted

select * from ProjectCopy

END

GO

select * from ProjectCopy

go

delete from ProjectCopy where Dnum = 4

98


T-SQL TRIGGERS

Example3. Employees should not work more than 40 hrs/week

-- See trigger code on next page ⇒⇒⇒⇒

select * , 'Before insert' from works_on where essn = 123456789GO

BEGIN TRANSACTION

-- Testing the trigger Trg_NoOverload

insert into works_on values (123456789,10,60)


GO

select *, 'After insert' from works_on where essn = 123456789

99


T-SQL TRIGGERS

DROP TRIGGER Trg_NoOverload GO

CREATE TRIGGER Trg_NoOverload ON WORKS_ON AFTER INSERTAS BEGIN

declare @essn integer, @totalHours float, @Problems int

declare curHours cursor forselect essn, sum(Hours) as totalHours from works_on where essn in (select essn from inserted)group by essn

--just for testing/debugging

select *, 'inserted' from insertedselect *, 'deleted' from deletedselect essn, sum(Hours) as totalHours from works_on group by essn

100


T-SQL TRIGGERS

-- CONTINUATION OF: CREATE TRIGGER Trg_NoOverload ON WORKS_ON…

--check if currently inserted records exceed sum-hours > 40

set @Problems = 0

if OBJECT_ID('curHours') is not nullDeallocate curHours

open curHoursfetch from curHours into @essn, @totalHourswhile (@@fetch_status = 0) begin

if (@totalHours > 40) beginset @Problems = 1raiserror ('Violation to rule: max 40 hrs/week %d ',17,55,@essn)end

fetch from curHours into @essn, @totalHoursend

if @Problems = 1 rollback transactionEND

101


T-SQL TRIGGERS

Example3. Employees should not work more than 40 hrs/week

Original WORKS_ON records for 123456789

INSERTED table

DELETED table

WORKS_ON table as seen internally by the trigger after performing the insertion ( just before rollback ).

102


T-SQL TRIGGERS

The UPDATE( ) Function

Returns a Boolean value that indicates whether an INSERT or UPDATEattempt was made on a specified column of a table or view.

UPDATE() is used anywhere inside the body of a Transact-SQL INSERT or UPDATE trigger to test whether the trigger should execute certain actions.

Syntax

UPDATE ( column )

103


T-SQL TRIGGERS

Example4. Using the UPDATE( ) function

CREATE TRIGGER Trg_SpyUpdateFunction

ON ProjetCopy AFTER UPDATE, INSERT

AS BEGIN


select 'inserted', * from inserted

select 'deleted', * from deleted

select * from ProjetCopy

if UPDATE(pLocation) print 'Location was changed'

if UPDATE(pName) print 'Project name was changed'

END

GO

select * from ProjetCopy where dnum = 4

go

update ProjetCopy set pLocation = 'Cleveland' where dnum = 4

104


T-SQL TRIGGERS

Example4. Using the UPDATE( ) function

update ProjetCopy set pLocation = 'Cleveland' where Dnum = 4

105


T-SQL TRIGGERS

CASCADED updates and deletesTriggers can be used to enforce non-elementary cases of referential integrity

ExampleDelete an employee may imply a complex sequence of operations including

- Erase family members (or perhaps save records in a historical table)- Remove all his assignments- If the employee is a supervisor, find his immediate supervisor and assign

him/her (at least temporarily) to his supervisees

106


T-SQL TRIGGERS

Example1. CASCADED updates and deletesPreparation for demonstrating the removal of dependents

-- is there already a temp #FAMILY table?. If not you must create it

if not exists(select * from tempdb..sysobjects where name like '#Family%')

begin

select * into #Family from DependentCopy where essn = 0

delete from #Family

end

Go

drop table DependentCopy

drop table EmployeeCopy

Go

--make copies of the Employee and Dependent tables

select * into DependentCopy from Dependent

select * into EmployeeCopy from Employee

Go

drop trigger trg_RemoveFamily

Go

107


T-SQL TRIGGERS

Example1. CASCADED updates and deletes (cont.)

create trigger trg_RemoveFamily on EMPLOYEEcopy after delete

as begin

-- copy dependent rec. into #Family for each deleted employee

insert into #family select * from DependentCopy

where essn in (select ssn from deleted)

-- now remove those dependent records

delete from DependentCopy

where essn in (select ssn from deleted)

if @@error <> 0 begin

raiserror('Problem during removal of family records',17,55)

rollback tran

end

end

go

select 'DependentCopy before',* from dependentCopy

go

delete from EmployeeCopy where ssn in (123456789, 987654321)

go

select '#Family', * from #Family

select 'DependentCopy after',* from DependentCopy

select 'EmployeeCopy', * from EmployeeCopy

108


T-SQL TRIGGERS

Example1. CASCADED updates and deletes (cont.)Removing Employees (123456789 & 987654321) and cascading on Dependents

109


T-SQL TRIGGERS

Example2. CASCADED updates and deletes

Business rule: If a supervisor is removed her immediate supervisor should be automatically assigned to her supervisees.

--make the supervisor of a removed supervisor take charge

create trigger trg_NewBoss on EMPLOYEECOPY after Delete

as begin

declare @boss nvarchar(50), @biggerBoss nvarchar(50)

declare curBiggerBoss cursor for

select distinct b.ssn as boss, b.superssn as biggerBoss

from Deleted b

open curBiggerBoss

fetch from curBiggerBoss into @boss, @biggerBoss

while @@fetch_status = 0 begin

update employeeCopy set superssn = @biggerBoss where superssn = @boss

fetch from curBiggerBoss into @boss, @biggerBoss

end

close curBiggerBoss

end

110


T-SQL TRIGGERS

Example2. CASCADED updates and deletes

-- preparation and testing

drop table employeeCopy

select 'before' , * into employeeCopy

from employee

Go

-- delete wakes up the trigger

delete from employeecopy

where ssn = 987654321

Go

-- show results

select ' after', ssn,superssn from employeecopy

sql server tsql [read-only] - csuohio.educis.csuohio.edu/~sschung/ist331/sql_server_tsql.pdf ·...

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