Steffen Goeldner

NAME

DBD::ADO - A DBI driver for Microsoft ADO (Active Data Objects)

SYNOPSIS

  use DBI();

  my $dbh = DBI->connect("dbi:ADO:$dsn", $usr, $pwd, $att ) or die $DBI::errstr;

DESCRIPTION

The DBD::ADO module supports ADO access on a Win32 machine. DBD::ADO is written to support the standard DBI interface to data sources.

PREREQUISITES

It is recommended that you use recent versions of the following prerequisites:

DBI
  http://search.cpan.org/~timb/DBI/
Win32::OLE
  http://search.cpan.org/~jdb/Win32-OLE/
ADO
  http://msdn.microsoft.com/data/

DBI Methods

connect

Use the DBI connect method to establish a database connection:

  my $dbh = DBI->connect("dbi:ADO:$dsn", $usr, $pwd, $att ) or die $DBI::errstr;

where

  $dsn - is an ADO ConnectionString
  $usr - is a user name
  $pwd - is a password
  $att - is a hash reference with additional attributes

Typical connection attributes are

  RaiseError => 1
  PrintError => 0
  AutoCommit => 0

See the DBI module documentation for full details.

Driver specific connection attributes are:

  ado_ConnectionTimeout
  ado_Mode

These attributes initialize the corresponding ADO Connection properties before opening the connection.

An ADO ConnectionString usually contains either a 'Provider' or a 'File Name' argument. If you omit these arguments, Provider defaults to MSDASQL (Microsoft OLE DB Provider for ODBC). Therefore you can pass an ODBC connection string (with DSN or DSN-less) as valid ADO connection string. If you use the OLE DB Provider for ODBC, it may be better to omit this additional layer and use DBD::ODBC with the ODBC driver.

In addition the following attributes may be set in the connection string:

  Attributes
  CommandTimeout
  ConnectionString
  ConnectionTimeout
  CursorLocation
  DefaultDatabase
  IsolationLevel
  Mode

Warning: This feature is supported for backward compatibility. It's saver to use the driver specific attributes described above. Anyway, the application is responsible for passing the correct values when setting any of these attributes.

See the ADO documentation for more information on connection strings.

ADO ConnectionString examples:

  test
  File Name=test.udl
  Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\data\test.mdb
  Provider=VFPOLEDB;Data Source=C:\data\test.dbc
  Provider=MSDAORA

For more examples, see e.g.:

  http://www.able-consulting.com/tech.htm

data_sources

Because ADO doesn't provide a data source repository, DBD::ADO uses it's own. It tries to load Local::DBD::ADO::DSN and expects an array of hashes describing the data sources. See ex/Local/DBD/ADO/DSN.pm for an example.

Warning: This is experimental and may change.

Warning: Check for the unlikly case that a file Local/DBD/ADO/DSN.pm exists in your module search path which causes unwanted side effects when loaded.

prepare

The prepare methods allows attributes (see DBI):

  $sth = $dbh->prepare( $statement )          or die $dbh->errstr;
  $sth = $dbh->prepare( $statement, \%attr )  or die $dbh->errstr;

DBD::ADO's prepare() supports setting the CursorType, e.g.:

  $sth = $dbh->prepare( $sql, { ado_cursortype => 'adOpenForwardOnly' } ) ...
  # the CursorType attribute is deprecated:
  $sth = $dbh->prepare( $sql, { CursorType     => 'adOpenForwardOnly' } ) ...

Possible cursortypes are:

  adOpenForwardOnly (default)
  adOpenKeyset
  adOpenDynamic
  adOpenStatic

It may be necessary to prepare the statement using cursortype 'adOpenStatic' when using a statement handle within a statement handle:

  while( my $table = $sth1->fetchrow_hashref ) {
    ...
    my $col = $sth2->fetchrow_hashref;
    ...
  }

Changing the CursorType is a solution to the following problem:

  Can't execute statement 'select * from authors':
  Lasterror : -2147467259
  OLE exception from "Microsoft OLE DB Provider for SQL Server":

  Cannot create new connection because in manual or distributed transaction
  mode.

  Win32::OLE(0.1403) error 0x80004005: "Unspecified error"
      in METHOD/PROPERTYGET "Open"

          Description : Cannot create new connection because in manual or distributed transaction mode.
          HelpContext : 0
          HelpFile    :
          NativeError : 0
          Number      : -2147467259
          Source      : Microsoft OLE DB Provider for SQL Server
          SQLState    :

bind_param

Normally, the datatypes of placeholders are known after the statement is prepared. In this case, you don't need to provide any type information:

  $sth->bind_param( 1, $value );

Sometimes, you need to specify a type for the parameter, e.g.:

  $sth->bind_param( 1, $value, SQL_NUMERIC );

As a last resort, you can provide an ADO-specific type, e.g.:

  $sth->bind_param( 1, $value, { ado_type => 6 } );  # adCurrency

If no type is given (neither by the provider nor by you), the datatype defaults to SQL_VARCHAR (adVarChar).

bind_param_inout

This can be utilized (with IN parameters) to support simple call-by-reference, allowing for lazy parameter binding.

  $sth->bind_param_inout( 1, \$value, 1024 );

The contents of $value will not be dereferenced until the call to $sth->execute(); is made. To use IN/OUT parameter types with stored procedures, remember that you will need to specify the appropriate command type when preparing the statement, e.g.:

  $sth = $dbh->prepare('sproc_name', { CommandType => 'adCmdStoredProc' } );

After execution, all call-by-reference parameters will be updated with the parameter values reported by the ADO command object.

For stored procedures, the parameter at index 0 is treated as the return value of the procedure. After execution, it is copied to the $sth->{ado_returnvalue} attribute.

Type info

There exists two implementations of type_info_all(). Which version is used depends on the ado_ti_ver database handle attribute:

$dbh->{ado_ti_ver} = 1

The first implementations tries to find for various DBI types a set of ADO types supported by the provider. The algorithm is highly sophisticated. It tends to generate more duplicate type codes and names.

$dbh->{ado_ti_ver} = 2 (default)

The second implementations is quite straightforward. It uses the set which the provider returns and tries to map various ADO codes to DBI/ODBC codes. The mapping is similar to the one used in column_info(). Duplicate type codes and names tend to occur less often. The rows are ordered by DATA_TYPE, but not necessarily by 'how closely each type maps to the corresponding ODBC SQL data type'. This second sort criterion is difficult to achieve.

table_info

  $sth = $dbh->table_info( $catalog, $schema, $table, $type, \%attr );
  $sth = $dbh->table_info( \%attr );  # deprecated

  $sth = $dbh->table_info( undef, undef, undef,'VIEW', {
    ado_columns      => 1,
    ado_trim_catalog => 0,
    ado_filter       => q{TABLE_NAME LIKE 'C%'},
  } );

Returns an active statement handle that can be used to fetch information about tables and views that exist in the database. By default the handle contains the columns described in the DBI documentation:

  TABLE_CAT, TABLE_SCHEM, TABLE_NAME, TABLE_TYPE, REMARKS

DBD::ADO allows selection criteria to be specified in the attributes hash for backward compatibility. In this way the record set can be restricted, for example, to only include tables of type 'VIEW':

  %attr = ( TABLE_TYPE => 'VIEW')  # deprecated

You can add criteria for any of the following columns:

  TABLE_CAT, TABLE_SCHEM, TABLE_NAME, TABLE_TYPE
ado_filter (deprecated: Filter)

DBD::ADO also allows the recordset to be filtered on a criteria string: a string made up of one or more individual clauses concatenated with AND or OR operators.

  %attr = ( ado_filter => q{TABLE_TYPE LIKE 'SYSTEM%'} )

The criteria string is made up of clauses in the form FieldName-Operator-Value. This is more flexible than using column criteria in that the filter allows a number of operators:

  <, >, <=, >=, <>, =, or LIKE

The Fieldname must be one of the ADO 'TABLES Rowset' column names:

  TABLE_CATALOG, TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, DESCRIPTION,
  TABLE_GUID, TABLE_PROPID, DATE_CREATED, DATE_MODIFIED

Value is the value with which you will compare the field values (for example,'Smith', #8/24/95#, 12.345, or $50.00). Use single quotes with strings and pound signs (#) with dates. For numbers, you can use decimal points, dollar signs, and scientific notation. If Operator is LIKE, Value can use wildcards. Only the asterisk (*) and percent sign (%) wild cards are allowed, and they must be the last character in the string. Value cannot be null.

ado_columns (deprecated: ADO_Columns)

Additional ADO-only fields will be included if the ado_columns attribute is set to true:

  %attr = ( ado_columns => 1 );
ado_trim_catalog (deprecated: Trim_Catalog)

Some ADO providers include path info in the TABLE_CAT column. This information will be trimmed if the ado_trim_catalog attribute is set to true:

  %attr = ( ado_trim_catalog => 1 );

tables

  @names = $dbh->tables(  $catalog, $schema, $table, $type, \%attr );

Returns a list of table and view names. Accepts any of the attributes described in the "table_info" method:

  @names = $dbh->tables( undef, undef, undef,'VIEW');

statistics_info

The row for TYPE 'table' is always the first row. Its PAGES field will be NULL (undef).

The $quick argument is ignored.

ADO-specific methods

ado_open_schema

  $sth = $dbh->ado_open_schema( $QueryType, @Criteria ) or die ...;

This method can be used to obtain database schema information from the provider. It returns a valid statement handle upon success.

$QueryType may be any valid ADO SchemaEnum name such as

  adSchemaTables
  adSchemaIndexes
  adSchemaProviderTypes

@Criteria (optional) is a list of query constraints depending on each $QueryType.

Example:

  my $sth = $dbh->ado_open_schema('adSchemaCheckConstraints','Catalog1');

Note: With DBI version 1.36 and earlier, the func() method has to be used to call private methods implemented by the driver:

  $h->func( @func_arguments, $func_name ) or die ...;

where $func_name is 'ado_open_schema'. You can use 'OpenSchema' for backward compatibility.

Example:

  my $sth = $dbh->func('adSchemaCheckConstraints','Catalog1','OpenSchema');

See ex/OpenSchema.pl for a working example.

Error handling

An ADO provider may return a collection of more than one error. After stringification , DBD::ADO concatenates these error messages to set the errstr value of the handle. However, the err value is set to the LastError known to Win32::OLE. Usually, this is the native OLE DB error code. These codes contain the following severity codes (see oledberr.h from the MDAC SDK):

  00 - Success
  01 - Informational
  10 - Warning
  11 - Error

The err value is set to 0 if all error codes belong to the Success or Informational category, which doesn't trigger the normal DBI error handling mechanisms.

The standard SQLSTATE is seldom supported by ADO providers and cannot be relied on.

The db/st handle attribute 'ado_max_errors' limits the number of errors extracted from the errors collection. To avoid time-consuming processing of huge error collections, it defaults to 50.

ADO specific attributes

ado_commandtimeout (all handles, decimal, inherited)

This attribute indicates the time (in seconds) after which a command is canceled. Typically, cancellation may occur during a long running execute method. Not all ADO providers support this functionality. Whereas ADO's Command object doesn't inherit the Connection's CommandTimeout setting, DBD::ADO's statement handle is initialized with the ado_commandtimeout attribute of its associated database handle.

LOB support

Since version 2.92, DBD::ADO supports the DBI handle attributes LongReadLen and LongTruncOk. LongReadLen defaults to 2147483647 (for backwards compatibility).

For multibyte strings, it's unspecified whether LongReadLen means bytes or characters. It's passed through to ADO's GetChunk method and ActualSize property.

Caveat: Unexpected truncation errors may occur if the ADO provider (e.g. Microsoft.Jet.OLEDB.4.0) uses bytes for ActualSize but characters for GetChunk.

Caveat: The ADO provider may have problems if the long field isn't the last one in the list of selected columns, e.g.:

  Description : Catastrophic failure
  HelpContext : 5000000
     HelpFile :
  NativeError :
       Number : -2147418113
       Source : Microsoft JET Database Engine
     SQLState :

The (experimental) blob_read method ignores the $offset argument for long fields (ADO maintains a current offset internally). To ensure that blob_read reads from the beginning, LongReadLen must be set to 0.

CAVEATS

Character set

Proper Unicode support depends on all components involved in your application: the DBMS, the ADO provider, Perl and some perl modules.

In short: Perl 5.8 and Win32::OLE 0.16 (or later) are strongly recommended and Win32::OLE has to be prepared to use the correct codepage:

  Win32::OLE->Option( CP => Win32::OLE::CP_UTF8 );

More detailed notes can be found at

  http://purl.net/stefan_ram/pub/perl_unicode_en

ADO providers

SQLOLEDB may truncate inserted strings

It seems that the size of the first inserted string is sticky. Inserted strings longer than the first one are truncated.

As a workaround, the ado_size attribute for bind_param was introduced in version 2.95:

  $sth->bind_param( $p_num, $bind_value, { ado_size => $size } );
MSDAORA may have problems with client-side cursors

MSDAORA may throw an error, return an empty result set or loop forever when CursorLocation is set to adUseClient. This setting is used in catalog methods for sorting and filtering.

AUTHORS

Tim Bunce and Phlip. With many thanks to Jan Dubois and Jochen Wiedmann for additions, debuggery and general help. Special thanks to Thomas Lowery, who maintained this module 2001-2003. Current maintainer is Steffen Goeldner.

SUPPORT

This software is supported via the dbi-users mailing list. For more information and to keep informed about progress you can join the mailing list by sending a message to dbi-users-help@perl.org

Please post details of any problems (or changes you needed to make) to dbi-users@perl.org and CC them to me (sgoeldner@cpan.org).

COPYRIGHT

  Copyright (c) 1998, Tim Bunce
  Copyright (c) 1999, Tim Bunce, Phlip, Thomas Lowery
  Copyright (c) 2000, Tim Bunce, Thomas Lowery
  Copyright (c) 2001, Tim Bunce, Thomas Lowery, Steffen Goeldner
  Copyright (c) 2002, Thomas Lowery, Steffen Goeldner
  Copyright (c) 2003, Thomas Lowery, Steffen Goeldner
  Copyright (c) 2004-2011 Steffen Goeldner

  All rights reserved.

  You may distribute under the terms of either the GNU General Public
  License or the Artistic License, as specified in the Perl README file.

SEE ALSO

Books

  ADO Reference book:  ADO 2.0 Programmer's Reference
  David Sussman and Alex Homer
  Wrox
  ISBN 1-861001-83-5

  ADO: ActiveX Data Objects
  Jason T. Roff
  O'Reilly
  ISBN 1-56592-415-0
  http://www.oreilly.com/catalog/ado/index.html

If there's anything better please let me know.

Perl modules

DBI, DBD::ODBC, Win32::OLE




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