Transcript ODBC: Open DataBase Connectivity

The Third Annual Perl Conference, 1999
OLE and ODBC: Taming
the Technologies
ODBC
Roth Consulting
Sunday, August 22, 1999
ODBC: Open DataBase
Connectivity
• Uses SQL
• Requires ODBC to be installed
• Win32::ODBC supports access into the ODBC
API
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ODBC 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?
• Unbelievable amount of Perl and ODBC use
–
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Database maintenance
Administration
Web commerce
Inter/intranet data access
• Professional Applications
– Digital Paper’s Intranet Docs (IDOC) product
•
•
•
•
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Can serve up to 2 million documents
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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 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 Name II
• Create manually using the ODBC control panel
applet
• Create using Win32::ODBC::ConfigDSN()
ConfigDSN( $Action, $Driver, $Attrib1, $Attribn )
– Actions
ODBC_ADD_DSN
ODBC_MODIFY_DSN
ODBC_REMOVE_DSN
ODBC_ADD_SYS_DSN
ODBC_MODIFY_SYS_DSN
ODBC_REMOVE_SYS_DSN
Add new DSN
Modify existing DSN
Remove existing DSN
Add new system DSN
Modify existing system DSN
Remove existing system DSN
– Driver depends upon installed drivers (keys from
Win32::ODBC::Drivers() ):
Microsoft Access Driver (*.mdb)
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DSN: Data Source Name III
– 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
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DSN: Data Source Name IV
use 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" );
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Connecting
• 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 Statement
• Submit a text based SQL query
$Result = $db->Sql( “SELECT * FROM Foo” );
• This is the only method call which returns a nonfalse value upon failure
– Returns error number (ODBC driver specific; not really
valuable)
– Call $db->Error() for more error details
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Fetching Results
• Call FetchRow() until it returns false
• Collect the data with Data() or DataHash()
while( $db->FetchRow() )
{
my( %Data ) = $db->DataHash();
…process data…
}
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Batch 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 Connection
• To close the database connection call Close()
$db->Close();
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Transactions
• 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 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 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 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 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 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 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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Other 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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