The ODBC session

OLE and ODBC: Taming OLE and ODBC: Taming the Technologiesthe Technologies

The Third Annual Perl Conference, 1999

Sunday, August 22, 1999Roth Consulting

ODBCODBC

Roth Consulting OLE and ODBC: Taming the Technologies (ODBC)

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• Uses SQL• Requires ODBC to be installed• Win32::ODBC supports access into the ODBC

API

ODBC: Open DataBase ODBC: Open DataBase ConnectivityConnectivity


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ODBC OptionsODBC Options• Perl can access ODBC

– Win32::OLE ( OLEDB, ADO )• Memory & processor overhead

• Not guaranteed to be ODBC or SQL

• Some bugs yet to be ironed out (eg. SQL Server and multiple text columns)

– ODBCTie• Is this still maintained?

– DBI• General DBI rules apply

• Cross platform

– Win32::ODBC• Requires Win32 machine


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Who uses Perl and ODBC?Who uses Perl and ODBC?• Unbelievable amount of Perl and ODBC use

– Database maintenance

– Administration

– Web commerce

– Inter/intranet data access

• Professional Applications– Digital Paper’s Intranet Docs (IDOC) product

• Partner with Xerox

• 99% Perl based

• Can serve up to 2 million documents

• http://www.xes.com/usa/products/doc_man/intradoc.htm


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What drivers are installed?What drivers are installed?• Enumerate installed ODBC drivers with:

%Drivers = Win32::ODBC::Drivers()

– Returns a hash

– Hash keys are driver names

– Hash value is string with driver specific attributes delimited by semicolons:

“Attrib1=Value1;Attrib2=Value2;Attribn=Valuen”


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DSN: Data Source NameDSN: Data Source Name• All database connections begin with a DSN• Named database configuration• Three types:

– User DSN

– System DSN

– File DSN

• Win 95/98 only understand User and File• When used as a CGI/ASP script with a web server

always use System DSN!


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DSN: Data Source NameDSN: Data Source Name• Create manually using the ODBC control panel applet• Create using Win32::ODBC::ConfigDSN()

ConfigDSN( $Action, $Driver, $Attrib1, $Attribn )

– ActionsODBC_ADD_DSN Add new DSNODBC_MODIFY_DSN Modify existing DSNODBC_REMOVE_DSN Remove existing DSNODBC_ADD_SYS_DSN Add new system DSNODBC_MODIFY_SYS_DSN Modify existing system DSNODBC_REMOVE_SYS_DSN Remove existing system DSN

– Driver depends upon installed drivers (keys from Win32::ODBC::Drivers() ):

Microsoft Access Driver (*.mdb)

IIII


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DSN: Data Source NameDSN: Data Source Name– Attributes are any valid ODBC driver keywords

• One required keyword:– DSN=Foo

• Other keywords differ based on ODBC driver

• Best way to discover keywords is by reading docs or manually creating a DSN then examining the Registry

• Do not include a “Driver” keyword

IIIIII


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DSN: Data Source NameDSN: Data Source Nameuse Win32::ODBC;

# Create a DSN...

Win32::ODBC::ConfigDSN( ODBC_ADD_DSN,

$Driver,

"DSN=My DSN Name",

"Description=A Test DSN",

"DBQ=c:\\temp\\$MyData.mdb",

"DEFAULTDIR= C:\\Database",

"UID=Admin",

"PWD=Adminpassword" );

IVIV


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ConnectingConnecting• Create a new Win32::ODBC object:

$db = new Win32::ODBC( "My DSN" );

• The DSN can either be the name of a DSN or it can be a full connect string:– “My DSN”

– “DSN=My DSN;UID=Foo;PWD=Bar”

• If the DSN passed in is really a Win32::ODBC object then that object is “cloned”

$db2 = new Win32::ODBC( $db );

– $db2 is identical to $db but with different STMT’s

– Some database systems do not like such clones


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Executing SQL StatementExecuting SQL Statement• Submit a text based SQL query

$Result = $db->Sql( “SELECT * FROM Foo” );

• This is the only method call which returns a non-false value upon failure– Returns error number (ODBC driver specific; not really

valuable)

– Call $db->Error() for more error details


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• Call FetchRow() until it returns false• Collect the data with Data() or DataHash()while( $db->FetchRow() ){ my( %Data ) = $db->DataHash(); …process data… }

Fetching ResultsFetching Results


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Batch QueriesBatch Queries• If you submitted a batch query or a stored

procedure returns multiple result sets repeat the FetchRow() process until MoreResults() returns FALSE.do{ while( $db->FetchRow() ) { my( %Data ) = $db->DataHash(); …process data… }} while( $db->MoreResults() );


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Closing The ConnectionClosing The Connection• To close the database connection call Close()

$db->Close();


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TransactionsTransactions• By default an ODBC connection is in AutoCommit

mode– All transactions are committed to the database immediately

• Turn off AutoCommit mode with:$db->SetConnectOption( $db->SQL_AUTOCOMMIT,

$db->SQL_AUTOCOMMIT_OFF );

• Perform queries (select, insert, delete, update, etc)• To commit or rollback call Transact():

$db->Transact( $db->SQL_COMMIT );$db->Transact( $db->SQL_ROLLBACK );


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Row CountsRow Counts• Report number of rows in the result set with:

$db->RowCount();

• Not all ODBC drivers support it• Some ODBC drivers only support it for insert and

delete• Alternative is to issue a SQL count query:

SELECT Count(*) FROM Foo

– The result set is one row and one column containing a value which is the number of rows


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Connection OptionsConnection Options• You can set and query connection options with:

$db->GetConnectOption( $Option );$db->SetConnectOption( $Option, $Value );

• SetConnectOption() returns TRUE if successfully set and FALSE if it failed to set the option

• GetConnectOption() returns the current value of the specified option. It does not return any errors!


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Connection Option ExamplesConnection Option Examples• To discover the current qualifier (SQL Server this is

the database, in Access it is the .mdb file):$Row = $db->GetConnectOption( $db-> SQL_CURRENT_QUALIFIER );

• To change the login timeout value (in seconds):$db->SetConnectOption( $db->SQL_LOGIN_TIMEOUT, 10 );

• Query the ODBC trace log file:$db->GetConnectOption( $db->SQL_OPT_TRACEFILE );

• Set ODBC trace logging to on:$db->SetConnectOption( $db->SQL_OPT_TRACE,

$db->SQL_OPT_TRACE_ON );


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Special Connect OptionsSpecial Connect Options• Some connection options must be set before the

connection to the database is performed• Pass these into the new() function:

$db = new Win32::ODBC( $Dsn,ODBC::SQL_LOGIN_TIMEOUT => 10,ODBC::SQL_OPT_TRACEFILE => ‘c:\trace.log’,ODBC::SQL_OPT_TRACE =>

ODBC::SQL_OPT_TRACE_ON );


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Stmt OptionsStmt Options• Every time you submit a command to the database

(such as a query) call it a statement or a stmt (for short)

• You can set and query options for stmt’s with:$db->GetStmtOption( $Option );$db->SetStmtOption( $Option, $Value );

• SetStmtOption() returns TRUE if successfully set and FALSE if it failed to set the option

• GetStmtOption() returns the current value of the specified option. It does not return any errors!


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Stmt Option ExamplesStmt Option Examples• To discover the current row:

$Row = $db->GetStmtOption( $db->SQL_ROW_NUMBER );

• To change the query timeout value (in seconds):$db->SetStmtOption( $db->SQL_QUERY_TIMEOUT, 10 );

• Set the driver to not scan the query for escape clauses:$db->SetStmtOption( $db->SQL_NOSCAN,

$db->SQL_NOSCAN_ON );


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• Programming DBI, by Tim Bunce and Alligator Descartes, O’Reilly & Associates.

• Win32 Perl Programming: The Standard Extensions, Dave Roth, MacMillan Publishing.

• Win32 Scripting Journal, http://www.winntmag.com/newsletter/scripting/

• The Perl Journal, http://www.tpj.com/

Other Sources Of InformationOther Sources Of Information• Programming DBI, by Tim Bunce and Alligator Descartes,

O’Reilly & Associates.

• Win32 Perl Programming: The Standard Extensions, Dave Roth, MacMillan Publishing.

• Win32 Scripting Journal, http://www.winntmag.com/newsletter/scripting/

• The Perl Journal, http://www.tpj.com/


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The ODBC session

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