Martin J Evans > DBD-ODBC-1.23 > DBD::ODBC

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Module Version: 1.23   Source   Latest Release: DBD-ODBC-1.48

NAME ^

DBD::ODBC - ODBC Driver for DBI

VERSION ^

This documentation refers to DBD::ODBC version 1.22_2.

SYNOPSIS ^

  use DBI;

  $dbh = DBI->connect('dbi:ODBC:DSN', 'user', 'password');

See DBI for more information.

DESCRIPTION ^

Change log and FAQs

Please note that the change log has been moved to DBD::ODBC::Changes. To access this documentation, use perldoc DBD::ODBC::Changes.

The FAQs have also moved to DBD::ODBC::FAQ.pm. To access the FAQs use perldoc DBD::ODBC::FAQ.

Important note about the tests

Please note that some tests may fail or report they are unsupported on this platform. Notably Oracle's ODBC driver will fail the "advanced" binding tests in t/08bind2.t. These tests run perfectly under SQL Server 2000. This is normal and expected. Until Oracle fixes their drivers to do the right thing from an ODBC perspective, it's going to be tough to fix the issue. The workaround for Oracle is to bind date types with SQL_TIMESTAMP. Also note that some tests may be skipped, such as t/09multi.t, if your driver doesn't seem to support returning multiple result sets. This is normal.

Version Control

DBD::ODBC source code is under version control at svn.perl.org. If you would like to use the "bleeding" edge version, you can get the latest from svn.perl.org via Subversion version control. Note there is no guarantee that this version is any different than what you get from the tarball from CPAN, but it might be :)

You may read about Subversion at http://subversion.tigris.org

You can get a subversion client from there and check dbd-odbc out via:

   svn checkout http://svn.perl.org/modules/dbd-odbc/trunk <your directory name here>

Which will pull all the files from the subversion trunk to your specified directory. If you want to see what has changed since the last release of DBD::ODBC read the Changes file or use "svn log" to get a list of checked in changes.

Contributing

There are six main ways you may help with the development and maintenance of this module:

Submitting patches

Please use Subversion (see above) to get the latest version of DBD::ODBC from the trunk and submit any patches against that.

Please, before submitting a patch:

   svn update
   <try and included a test which demonstrates the fix/change working>
   <test your patch>
   svn diff > describe_my_diffs.patch

and send the resulting file to me and cc the dbi-users@perl.org mailing list (if you are not a member - why not!).

Reporting installs

Install CPAN::Reporter and report you installations. This is easy to do - see "CPAN Testers Reporting".

Report bugs

If you find what you believe is a bug then enter it into the http://rt.cpan.org/Dist/Display.html?Name=DBD-ODBC system. Where possible include code which reproduces the problem including any schema required and the versions of software you are using.

If you are unsure whether you have found a bug report it anyway or post it to the dbi-users mailing list.

pod comments and corrections

If you find inaccuracies in the DBD::ODBC pod or have a comment which you think should be added then go to http://annocpan.org and submit them there. I get an email for every comment added and will review each one and apply any changes to the documentation.

Review DBD::ODBC

Add your review of DBD::ODBC on http://cpanratings.perl.org.

If you are a member on ohloh then add your review or register your use of DBD::ODBC at http://www.ohloh.net/projects/perl_dbd_odbc.

submit test cases

Most DBDs are built against a single client library for the database.

Unlike other DBDs, DBD::ODBC works with many different ODBC drivers. Although they all should be written with regard to the ODBC specification drivers have bugs and in some places the specification is open to interpretation. As a result, when changes are applied to DBD::ODBC it is very easy to break something in one ODBC driver.

What helps enormously to identify problems in the many combinations of DBD::ODBC and ODBC drivers is a large test suite. I would greatly appreciate any test cases and in particular any new test cases for databases other than MS SQL Server.

DBI attribute handling

If a DBI defined attribute is not mentioned here it behaves as per the DBI specification.

ReadOnly (boolean)

DBI documents the ReadOnly attribute as being settleable and retrievable on connection and statement handles. In ODBC setting ReadOnly to true causes the connection attribute SQL_ATTR_ACCESS_MODE to be set to SQL_MODE_READ_ONLY and setting it to false will set the access mode to SQL_MODE_READ_WRITE (which is the default in ODBC).

Note: There is no equivalent of setting ReadOnly on a statement handle in ODBC.

Note: See ODBC documentation on SQL_ATTR_ACCESS_MODE as setting it to SQL_MODE_READ_ONLY does not prevent your script from running updates or deletes; it is simply a hint to the driver/database that you won't being doing updates.

This attribute requires DBI version 1.55 or better.

Private attributes common to connection and statement handles

odbc_ignore_named_placeholders

Use this if you have special needs (such as Oracle triggers, etc) where :new or :name mean something special and are not just place holder names. You must then use ? for binding parameters. Example:

 $dbh->{odbc_ignore_named_placeholders} = 1;
 $dbh->do("create trigger foo as if :new.x <> :old.x then ... etc");

Without this, DBD::ODBC will think :new and :old are placeholders for binding and get confused.

odbc_default_bind_type

This value defaults to 0.

Older versions of DBD::ODBC assumed that the parameter binding type was 12 (SQL_VARCHAR). Newer versions always attempt to call SQLDescribeParam to find the parameter types but if SQLDescribeParam is unavailable DBD::ODBC falls back to a default bind type. The internal default bind type is SQL_VARCHAR (for non-unicode build) and SQL_WVARCHAR (for a unicode build). If you set odbc_default_bind_type to a value other than 0 you override the internal default.

N.B If you call the bind_param method with a SQL type this overrides everything else above.

odbc_force_rebind

This is to handle special cases, especially when using multiple result sets. Set this before execute to "force" DBD::ODBC to re-obtain the result set's number of columns and column types for each execute. Especially useful for calling stored procedures which may return different result sets each execute. The only performance penalty is during execute(), but I didn't want to incur that penalty for all circumstances. It is probably fairly rare that this occurs. This attribute will be automatically set when multiple result sets are triggered. Most people shouldn't have to worry about this.

odbc_async_exec

Allow asynchronous execution of queries. This causes a spin-loop (with a small "sleep") until the ODBC API being called is complete (i.e., while the ODBC API returns SQL_STILL_EXECUTING). This is useful, however, if you want the error handling and asynchronous messages (see the "odbc_err_handler" and t/20SQLServer.t for an example of this.

odbc_query_timeout

This allows you to change the ODBC query timeout (the ODBC statement attribute SQL_ATTR_QUERY_TIMEOUT). ODBC defines the query time out as the number of seconds to wait for a SQL statement to execute before returning to the application. A value of 0 (the default) means there is no time out. Do not confuse this with the ODBC attributes SQL_ATTR_LOGIN_TIMEOUT and SQL_ATTR_CONNECTION_TIMEOUT. Add

  { odbc_query_timeout => 30 }

to your connect, set on the dbh before creating a statement or explicitly set it on your statement handle. The odbc_query_timeout on a statement is inherited from the parent connection.

Note that internally DBD::ODBC only sets the query timeout if you set it explicitly and the default of 0 (no time out) is implemented by the ODBC driver and not DBD::ODBC.

Note that some ODBC drivers implement a maximum query timeout value and will limit timeouts set above their maximum. You may see a warning if your time out is capped by the driver but there is currently no way to retrieve the capped value back from the driver.

Note that some drivers may not support this attribute.

See t/20SqlServer.t for an example.

odbc_putdata_start

odbc_putdata_start defines the size at which DBD::ODBC uses SQLPutData and SQLParamData to send larger objects to the database instead of simply binding them as normal with SQLBindParameter. It is mostly a placeholder for future changes allowing chunks of data to be sent to the database and there is little reason for anyone to change it currently.

The default for odbc_putdata_start is 32768 because this value was hard-coded in DBD::ODBC until 1.16_1.

odbc_column_display_size

If you ODBC driver does not support the SQL_COLUMN_DISPLAY_SIZE and SQL_COLUMN_LENGTH attributes to SQLColAtrributes then DBD::ODBC does not know how big the column might be. odbc_column_display_size sets the default value for the column size when retrieving column data where the size cannot be determined.

The default for odbc_column_display_size is 2001 because this value was hard-coded in DBD::ODBC until 1.17_3.

Private connection attributes

odbc_err_handler

NOTE: There should be no reason to use this now as there is a DBI attribute of a similar name. In future versions this attribute will be deleted.

Allow errors to be handled by the application. A call-back function supplied by the application to handle or ignore messages.

The callback function receives three parameters: state (string), error (string) and the native error code (number).

If the error handler returns 0, the error is ignored, otherwise the error is passed through the normal DBI error handling.

This can also be used for procedures under MS SQL Server (Sybase too, probably) to obtain messages from system procedures such as DBCC. Check t/20SQLServer.t and t/10handler.t.

  $dbh->{RaiseError} = 1;
  sub err_handler {
     ($state, $msg, $native) = @_;
     if ($state = '12345')
         return 0; # ignore this error
     else
         return 1; # propagate error
  }
  $dbh->{odbc_err_handler} = \$err_handler;
  # do something to cause an error
  $dbh->{odbc_err_handler} = undef; # cancel the handler

odbc_SQL_ROWSET_SIZE

Here is the information from the original patch, however, this could/has caused SQL Server to "lock up". Please use at your own risk!

SQL_ROWSET_SIZE attribute patch from Andrew Brown

  > There are only 2 additional lines allowing for the setting of
  > SQL_ROWSET_SIZE as db handle option.
  >
  > The purpose to my madness is simple. SqlServer (7 anyway) by default
  > supports only one select statement at once (using standard ODBC cursors).
  > According to the SqlServer documentation you can alter the default
  > setting of three values to force the use of server cursors - in
  > which case multiple selects are possible.
  >
  > The code change allows for:
  > $dbh->{SQL_ROWSET_SIZE} = 2;    # Any value > 1
  >
  > For this very purpose.
  >
  > The setting of SQL_ROWSET_SIZE only affects the extended fetch
  > command as far as I can work out and thus setting this option
  > shouldn't affect DBD::ODBC operations directly in any way.
  >
  > Andrew
  >

In versions of SQL Server 2008 and later see "Multiple Active Statements (MAS)" in the DBD::ODBC::FAQ instead of using this attribute.

odbc_exec_direct

Force DBD::ODBC to use SQLExecDirect instead of SQLPrepare/SQLExecute.

There are drivers that only support SQLExecDirect and the DBD::ODBC do() override does not allow returning result sets. Therefore, the way to do this now is to set the attribute odbc_exec_direct.

NOTE: You may also want to use this option if you are creating temporary objects (e.g., tables) in MS SQL Server and for some reason cannot use the do method. see http://technet.microsoft.com/en-US/library/ms131667.aspx which says Prepared statements cannot be used to create temporary objects on SQL Server 2000 or later.... Without odbc_exec_direct, the temporary object will disappear before you can use it.

There are currently two ways to get this:

    $dbh->prepare($sql, { odbc_exec_direct => 1});

and

    $dbh->{odbc_exec_direct} = 1;

NOTE: Even if you build DBD::ODBC with unicode support you can still not pass unicode strings to the prepare method if you also set odbc_exec_direct. This is a restriction in this attribute which is unavoidable.

SQL_DRIVER_ODBC_VER

This, while available via get_info() is captured here. I may get rid of this as I only used it for debugging purposes.

odbc_cursortype

This allows multiple concurrent statements on SQL*Server. In your connect, add

  { odbc_cursortype => 2 }.

If you are using DBI > 1.41, you should also be able to use

 { odbc_cursortype => DBI::SQL_CURSOR_DYNAMIC }

instead. For example:

    my $dbh = DBI->connect("dbi:ODBC:$DSN", $user, $pass,
                  { RaiseError => 1, odbc_cursortype => 2});
    my $sth = $dbh->prepare("one statement");
    my $sth2 = $dbh->prepare("two statement");
    $sth->execute;
    my @row;
    while (@row = $sth->fetchrow_array) {
       $sth2->execute($row[0]);
    }

See t/20SqlServer.t for an example.

odbc_has_unicode

A read-only attribute signifying whether DBD::ODBC was built with the C macro WITH_UNICODE or not. A value of 1 indicates DBD::ODBC was built with WITH_UNICODE else the value returned is 0.

Building WITH_UNICODE affects columns and parameters which are SQL_C_WCHAR, SQL_WCHAR, SQL_WVARCHAR, and SQL_WLONGVARCHAR, SQL, the connect method and a lot more. See "Unicode".

When odbc_has_unicode is 1, DBD::ODBC will:

bind columns the database declares as wide characters as SQL_Wxxx

This means that UNICODE data stored in these columns will be returned to Perl in UTF-8 and with the UTF8 flag set.

bind parameters the database declares as wide characters as SQL_Wxxx

Parameters bound where the database declares the parameter as being a wide character (or where the parameter type is explicitly set to a wide type - SQL_Wxxx) can be UTF8 in Perl and will be mapped to UTF16 before passing to the driver.

SQL

SQL passed to the prepare or do methods which has the UTF8 flag set will be converted to UTF16 before being passed to the ODBC APIs SQLPrepare or SQLExecDirect.

connection strings

Connection strings passed to the connect method will be converted to UTF16 before being passed to the ODBC API SQLDriverConnectW. This happens irrespective of whether the UTF8 flag is set on the perl connect strings because unixODBC requires an application to call SQLDriverConnectW to indicate it will be calling the wide ODBC APIs.

NOTE: You will need at least Perl 5.8.1 to use UNICODE with DBD::ODBC.

NOTE: Binding of unicode output parameters is coded but untested.

NOTE: When building DBD::ODBC on Windows ($^O eq 'MSWin32') the WITH_UNICODE macro is automatically added. To disable specify -nou as an argument to Makefile.PL (e.g. perl Makefile.PL -nou). On non-Windows platforms the WITH_UNICODE macro is not enabled by default and to enable you need to specify the -u argument to Makefile.PL. Please bare in mind that some ODBC drivers do not support SQL_Wxxx columns or parameters.

NOTE: Unicode support on Windows 64 bit platforms is currently untested. Let me know how you get on with it.

UNICODE support in ODBC Drivers differs considerably. Please read the README.unicode file for further details.

odbc_out_connect_string

After calling the connect method this will be the ODBC driver's out connection string - see documentation on SQLDriverConnect.

odbc_version

This was added prior to the move to ODBC 3.x to allow the caller to "force" ODBC 3.0 compatibility. It's probably not as useful now, but it allowed get_info and get_type_info to return correct/updated information that ODBC 2.x didn't permit/provide. Since DBD::ODBC is now 3.x, this can be used to force 2.x behavior via something like: my

  $dbh = DBI->connect("dbi:ODBC:$DSN", $user, $pass,
                      { odbc_version =>2});

Private statement attributes

odbc_more_results

Use this attribute to determine if there are more result sets available. SQL Server supports this feature. Use this as follows:

  do {
     my @row;
     while (@row = $sth->fetchrow_array()) {
        # do stuff here
     }
  } while ($sth->{odbc_more_results});

Note that with multiple result sets and output parameters (i.e,. using bind_param_inout, don't expect output parameters to be bound until ALL result sets have been retrieved.

Private DBD::ODBC Functions

You use DBD::ODBC private functions like this:

  $dbh->func(arg, private_function_name, @args);

GetInfo

This private function is now superceded by DBI's get_info method.

This function maps to the ODBC SQLGetInfo call and the argument should be a valid ODBC information type (see ODBC specification). e.g.

  $value = $dbh->func(6, 'GetInfo');

which returns the SQL_DRIVER_NAME.

This function returns a scalar value, which can be a numeric or string value depending on the information value requested.

SQLGetTypeInfo

This private function is now superceded by DBI's type_info and type_info_all methods.

This function maps to the ODBC SQLGetTypeInfo API and the argument should be a SQL type number (e.g. SQL_VARCHAR) or SQL_ALL_TYPES. SQLGetTypeInfo returns information about a data type supported by the data source.

e.g.

  use DBI qw(:sql_types);

  $sth = $dbh->func(SQL_ALL_TYPES, GetTypeInfo);
  DBI::dump_results($sth);

This function returns a DBI statement handle for the SQLGetTypeInfo result-set containing many columns of type attributes (see ODBC specification).

NOTE: It is VERY important that the use DBI includes the qw(:sql_types) so that values like SQL_VARCHAR are correctly interpreted. This "imports" the sql type names into the program's name space. A very common mistake is to forget the qw(:sql_types) and obtain strange results.

GetFunctions

This function maps to the ODBC SQLGetFunctions API which returns information on whether a function is supported by the ODBC driver.

The argument should be SQL_API_ALL_FUNCTIONS (0) for all functions or a valid ODBC function number (e.g. SQL_API_SQLDESCRIBEPARAM which is 58). See ODBC specification or examine your sqlext.h and sql.h header files for all the SQL_API_XXX macros.

If called with SQL_API_ALL_FUNCTIONS (0), then a 100 element array is returned where each element will contain a '1' if the ODBC function with that SQL_API_XXX index is supported or '' if it is not.

If called with a specific SQL_API_XXX value for a single function it will return true if the ODBC driver supports that function, otherwise false.

e.g.

    my @x = $dbh->func(0,"GetFunctions");
    print "SQLDescribeParam is supported\n" if ($x[58]);

or

    print "SQLDescribeParam is supported\n"
        if $dbh->func(58, "GetFunctions");

GetStatistics

This private function is now superceded by DBI's statistics_info method.

See the ODBC specification for the SQLStatistics API. You call SQLStatistics like this:

  $dbh->func($catalog, $schema, $table, $unique, 'GetStatistics');

Prior to DBD::ODBC 1.16 $unique was not defined as being true/false or SQL_INDEX_UNIQUE/SQL_INDEX_ALL. In fact, whatever value you provided for $unique was passed through to the ODBC API SQLStatistics call unchanged. This changed in 1.16, where $unique became a true/false value which is interpreted into SQL_INDEX_UNIQUE for true and SQL_INDEX_ALL for false.

GetForeignKeys

This private function is now superceded by DBI's foreign_key_info method.

See the ODBC specification for the SQLForeignKeys API. You call SQLForeignKeys like this:

  $dbh->func($pcatalog, $pschema, $ptable,
             $fcatalog, $fschema, $ftable,
             "GetForeignKeys");

GetPrimaryKeys

This private function is now superceded by DBI's primary_key_info method.

See the ODBC specification for the SQLPrimaryKeys API. You call SQLPrimaryKeys like this:

  $dbh->func($catalog, $schema, $table, "GetPrimaryKeys");

data_sources

This private function is now superceded by DBI's data_sources method.

You call data_sources like this:

  @dsns = $dbh->func("data_sources);

Handled since 0.21.

GetSpecialColumns

See the ODBC specification for the SQLSpecialColumns API. You call SQLSpecialColumns like this:

  $dbh->func($identifier, $catalog, $schema, $table, $scope,
             $nullable, 'GetSpecialColumns');

Handled as of version 0.28

head3 ColAttributes

This private function is now superceded by DBI's statement attributes NAME, TYPE, PRECISION, SCALE, NULLABLE etc).

See the ODBC specification for the SQLColAttributes API. You call SQLColAttributes like this:

  $dbh->func($column, $ftype, "ColAttributes");

  SQL_COLUMN_COUNT = 0
  SQL_COLUMN_NAME = 1
  SQL_COLUMN_TYPE = 2
  SQL_COLUMN_LENGTH = 3
  SQL_COLUMN_PRECISION = 4
  SQL_COLUMN_SCALE = 5
  SQL_COLUMN_DISPLAY_SIZE = 6
  SQL_COLUMN_NULLABLE = 7
  SQL_COLUMN_UNSIGNED = 8
  SQL_COLUMN_MONEY = 9
  SQL_COLUMN_UPDATABLE = 10
  SQL_COLUMN_AUTO_INCREMENT = 11
  SQL_COLUMN_CASE_SENSITIVE = 12
  SQL_COLUMN_SEARCHABLE = 13
  SQL_COLUMN_TYPE_NAME = 14
  SQL_COLUMN_TABLE_NAME = 15
  SQL_COLUMN_OWNER_NAME = 16
  SQL_COLUMN_QUALIFIER_NAME = 17
  SQL_COLUMN_LABEL = 18

Note:Oracle's ODBC driver for linux in instant client 11r1 often returns strange values for column name e.g., '20291'. It is wiser to use DBI's NAME and NAME_xx attributes for portability.

head3 DescribeCol

This private function is now superceded by DBI's statement attributes NAME, TYPE, PRECISION, SCLARE, NULLABLE etc).

See the ODBC specification for the SQLDescribeCol API. You call SQLDescribeCol like this:

  @info = $dbh->func($column, "DescribeCol");

The returned array contains the column attributes in the order described in the ODBC specification for SQLDescribeCol.

Tracing

DBD::ODBC now supports the parse_trace_flag and parse_trace_flags methods introduced in DBI 1.42 (see DBI for a full description). As of DBI 1.604, the only trace flag defined which is relevant to DBD::ODBC is 'SQL' which DBD::ODBC supports by outputting the SQL strings (after modification) passed to the prepare and do methods.

Currently DBD::ODBC supports two private trace flags. The 'odbcunicode' flag traces some unicode operations and the odbcconnection traces the connect process.

To enable tracing of particular flags you use:

  $h->trace($h->parse_trace_flags('SQL|odbcconnection'));
  $h->trace($h->parse_trace_flags('1|odbcunicode'));

In the first case 'SQL' and 'odbcconnection' tracing is enabled on $h. In the second case trace level 1 is set and 'odbcunicode' tracing is enabled.

If you want to enable a DBD::ODBC private trace flag before connecting you need to do something like:

  use DBD::ODBC;
  DBI->trace(DBD::ODBC->parse_trace_flag('odbcconnection'));

or

  use DBD::ODBC;
  DBI->trace(DBD::ODBC->parse_trace_flags('odbcconnection|odbcunicode'));

DBD::ODBC outputs tracing at levels 3 and above (as levels 1 and 2 are reserved for DBI).

For comprehensive tracing of DBI method calls without all the DBI internals see DBIx::Log4perl.

Deviations from the DBI specification

Mixed placeholder types

There are 3 conventions for place holders in DBI. These are '?', ':N' and ':name' (where 'N' is a number and 'name' is an alpha numeric string not beginning with a number). DBD::ODBC supports all these methods for naming placeholders but you must only use one method throughout a particular SQL string. If you mix placeholder methods you will get an error like:

  Can't mix placeholder styles (1/2)

Using the same placeholder more than once

DBD::ODBC does not support (currently) the use of one named placeholder more than once in the a single SQL string. i.e.,

  insert into foo values (:bar, :p1, :p2, :bar);

is not supported because 'bar' is used more than once but:

  insert into foo values(:bar, :p1, :p2)

is ok. If you do the former you will get an error like:

  DBD::ODBC does not yet support binding a named parameter more than once

Binding named placeholders

Although the DBI documentation (as of 1.604) does not say how named parameters are bound Tim Bunce has said that in Oracle they are bound with the leading ':' as part of the name and that has always been the case. i.e.,

  prepare("insert into mytable values (:fred)");
  bind_param(":foo", 1);

DBD::ODBC does not support binding named parameters with the ':' introducer. In the above example you must use:

  bind_param("foo", 1);

In discussion on the dbi-dev list is was suggested that the ':' could be made optional and there were no basic objections but it has not made it's way into the pod yet.

Sticky Parameter Types

The DBI specification post 1.608 says in bind_param:

  The data type is 'sticky' in that bind values passed to execute()
  are bound with the data type specified by earlier bind_param()
  calls, if any.  Portable applications should not rely on being able
  to change the data type after the first C<bind_param> call.

DBD::ODBC does allow a parameter to be rebound with another data type as ODBC inherently allows this. Therefore you can do:

  # parameter 1 set as a SQL_LONGVARCHAR
  $sth->bind_param(1, $data, DBI::SQL_LONGVARCHAR);
  # without the bind above the $data parameter would be either a DBD::ODBC
  # internal default or whatever the ODBC driver said it was but because
  # parameter types are sticky, the type is still SQL_LONGVARCHAR.
  $sth->execute($data);
  # change the bound type to SQL_VARCHAR
  # some DBDs will ignore the type in the following, DBD::ODBC does not
  $sth->bind_param(1, $data, DBI::SQL_VARCHAR);

Unicode

The ODBC specification supports wide character versions (a postfix of 'W') of some of the normal ODBC APIs e.g., SQLDriverConnectW is a wide character version of SQLDriverConnect.

In ODBC on Windows the wide characters are defined as SQLWCHARs (2 bytes) and are UCS-2. On non-Windows, the main driver managers I know of have implemented the wide character APIs differently:

unixODBC

unixODBC mimics the Windows ODBC API precisely meaning the wide character versions expect and return 2-byte characters in UCS-2.

unixODBC will happily recognise ODBC drivers which only have the ANSI versions of the ODBC API and those that have the wide versions too.

unixODBC will allow an ANSI application to work with a unicode ODBC driver and vice versa (although in the latter case you obviously cannot actually use unicode).

unixODBC does not prevent you sending UTF-8 in the ANSI versions of the ODBC APIs but whether that is understood by your ODBC driver is another matter.

unixODBC differs in only one way from the Microsoft ODBC driver in terms of unicode support in that it avoids unnecessary translations between single byte and double byte characters when an ANSI application is using a unicode-aware ODBC driver by requiring unicode applications to signal their intent by calling SQLDriverConnectW first. On Windows, the ODBC driver manager always uses the wide versions of the ODBC API in ODBC drivers which provide the wide versions regardless of what the application really needs and this results in a lot of unnecessary character translations when you have an ANSI application and a unicode ODBC driver.

iODBC

The wide character versions expect and return wchar_t types.

DBD::ODBC has gone with unixODBC so you cannot use iODBC with a unicode build of DBD::ODBC. However, some ODBC drivers support UTF-8 (although how they do this with SQLGetData reliably I don't know) and so you should be able to use those with DBD::ODBC not built for unicode.

Enabling and Disabling Unicode support

On Windows Unicode support as ss enabled by default and to disable it you will need to specify -nou to Makefile.PL to get back to the original behavior of DBD::ODBC before any Unicode support was added.

e.g.,

  perl Makfile.PL -nou

On non-Windows platforms Unicode support is disabled by default. To enable it specify -u to Makefile.PL when you configure DBD::ODBC.

e.g.,

  perl Makefile.PL -u

Unicode - What is supported?

As of version 1.17 DBD::ODBC has the following unicode support:

SQL (introduced in 1.16_2)

Unicode strings in calls to the prepare and do methods are supported so long as the odbc_execdirect attribute is not used.

unicode connection strings (introduced in 1.16_2)

Unicode connection strings are supported but you will need a DBI post 1.607 for that.

column names

Unicode column names are returned.

bound columns (introduced in 1.15)

If the DBMS reports the column as being a wide character (SQL_Wxxx) it will be bound as a wide character and any returned data will be converted from UTF16 to UTF8 and the UTF8 flag will then be set on the data.

bound parameters

If the perl scalars you bind to parameters are marked UTF8 and the DBMS reports the type as being a wide type or you bind the parameter as a wide type they will be converted to wide characters and bound as such.

Since version 1.16_4, the default parameter bind type is SQL_WVARCHAR for unicode builds of DBD::ODBC. This only affects ODBC drivers which do not support SQLDescribeParam and only then if you do not specifically set a sql type on the bind_param method call.

The above Unicode support has been tested with the SQL Server, Oracle 9.2+ and Postgres drivers on Windows and various Easysoft ODBC drivers on UNIX.

Unicode - What is not supported?

You cannot use unicode parameter names e.g.,

  select * from table where column = :unicode_param_name

You cannot use unicode strings in calls to prepare if you set the odbc_execdirect attribute.

You cannot use the iODBC driver manager with DBD::ODBC built for unicode.

Unicode - Caveats

For Unicode support on any platform in Perl you will need at least Perl 5.8.1 - sorry but this is the way it is with Perl.

The Unicode support in DBD::ODBC expects a WCHAR to be 2 bytes (as it is on Windows and as the ODBC specification suggests it is). Until ODBC specifies any other Unicode support it is not envisioned this will change. On UNIX there are a few different ODBC driver managers. I have only tested the unixODBC driver manager (http://www.unixodbc.org) with Unicode support and it was built with defaults which set WCHAR as 2 bytes.

I believe that the iODBC driver manager expects wide characters to be wchar_t types (which are usually 4) and hence DBD::ODBC will not work iODBC when built for unicode.

The ODBC Driver must expect Unicode data specified in SQLBindParameter and SQLBindCol to be UTF16 in local endianess. Similarly, in calls to SQLPrepareW, SQLDescribeColW and SQLDriverConnectW.

You should be aware that once Unicode support is enabled it affects a number of DBI methods (some of which you might not expect). For instance, when listing tables, columns etc some drivers (e.g. Microsoft SQL Server) will report the column types as wide types even if the strings actually fit in 7-bit ASCII. As a result, there is an overhead for retrieving this column data as 2 bytes per character will be transmitted (compared with 1 when Unicode support is not enabled) and these strings will be converted into UTF8 but will end up fitting (in most cases) into 7bit ASCII so a lot of conversion work has been performed for nothing. If you don't have Unicode table and column names or Unicode column data in your tables you are best disabling Unicode support.

I am at present unsure if ChopBlanks processing on Unicode strings is working correctly on UNIX. If nothing else the construct L' ' in dbdimp.c might not work with all UNIX compilers. Reports of issues and patches welcome.

Unicode implementation in DBD::ODBC

DBD::ODBC uses the wide character versions of the ODBC API and the SQL_WCHAR ODBC type to support unicode in Perl.

Wide characters returned from the ODBC driver will be converted to UTF-8 and the perl scalars will have the utf8 flag set (by using sv_utf8_decode).

perl scalars which are UTF-8 and are sent through the ODBC API will be converted to UTF-16 and passed to the ODBC wide APIs or signalled as SQL_WCHARs (e.g., in the case of bound columns).

When built for unicode, DBD::ODBC will always call SQLDriverConnectW (and not SQLDriverConnect) even if a) your connection string is not unicode b) you have not got a DBI later than 1.607, because unixODBC requires SQLDriverConnectW to be called if you want to call other unicode ODBC APIs later. As a result, if you build for unicode and pass ASCII strings to the connect method they will be converted to UTF-16 and passed to SQLDriverConnectW. This should make no real difference to perl not using unicode connection strings.

You will need a DBI later than 1.607 to support unicode connection strings because until post 1.607 there was no way for DBI to pass unicode strings to the DBD.

Unicode and Oracle

You have to set the environment variables NLS_NCHAR=AL32UTF8 and NLS_LANG=AMERICAN_AMERICA.AL32UTF8 (or any other language setting ending with .AL32UTF8) before loading DBD::ODBC to make Oracle return Unicode data. (See also "Oracle and Unicode" in the POD of DBD::Oracle.)

On Windows, using the Oracle ODBC Driver you have to enable the Force SQL_WCHAR support Workaround in the data source configuration to make Oracle return Unicode to a non-Unicode application. Alternatively, you can include FWC=T in your connect string.

Unless you need to use ODBC, if you want Unicode support with Oracle you are better off using DBD::Oracle.

Unicode and PostgreSQL

Some tests from the original DBD::ODBC 1.13 fail with PostgreSQL 8.0.3, so you may not want to use DBD::ODBC to connect to PostgreSQL 8.0.3.

Unicode tests fail because PostgreSQL seems not to give any hints about Unicode, so all data is treated as non-Unicode.

Unless you need to use ODBC, if you want Unicode support with Postgres you are better off with DBD::Pg as it has a specific attribute named pg_enable_utf8 to enable Unicode support.

Unicode and Easysoft ODBC Drivers

We have tested the Easysoft SQL Server, Oracle and ODBC Bridge drivers with DBD::ODBC built for Unicode. All work as described without modification except for the Oracle driver you will need to set you NLS_LANG as mentioned above.

Unicode and other ODBC drivers

If you have a unicode-enabled ODBC driver and it works with DBD::ODBC let me know and I will include it here.

ODBC Support in ODBC Drivers

Drivers without SQLDescribeParam

Some drivers do not support the SQLDescribeParam ODBC API (e.g., Microsoft Access).

DBD::ODBC uses the SQLDescribeParam API when parameters are bound to your SQL to find the types of the parameters. If the ODBC driver does not support SQLDescribeParam, DBD::ODBC assumes the parameters are SQL_VARCHAR or SQL_WVARCHAR types (depending on whether DBD::ODBC is built for unicode or not). In any case, if you bind a parameter and specify a SQL type this overrides any type DBD::ODBC would choose.

For ODBC drivers which do not support SQLDescribeParam the default behavior in DBD::ODBC may not be what you want. To change the default parameter bind type set "odbc_default_bind_type". If, after that you have some SQL where you need to vary the parameter types used add the SQL type to the end of the bind_param method.

  use DBI qw(:sql_types);
  $h = DBI->connect;
  # set the default bound parameter type
  $h->{odbc_default_bind_type} = SQL_VARCHAR;
  # bind a parameter with a specific type
  $s = $h->prepare(q/insert into mytable values(?)/);
  $s->bind_param(1, "\x{263a}", SQL_WVARCHAR);

CPAN Testers Reporting

Please, please, please (is that enough), consider installing CPAN::Reporter so that when you install perl modules a report of the installation success or failure can be sent to cpan testers. In this way module authors 1) get feedback on the fact that a module is being installed 2) get to know if there are any installation problems. Also other people like you may look at the test reports to see how successful they are before choosing the version of a module to install.

CPAN::Reporter is easy to install and configure like this:

  perl -MCPAN -e shell
  cpan> install CPAN::Reporter
  cpan> reload cpan
  cpan> o conf init test_report

Simply answer the questions to configure CPAN::Reporter.

You can find the CPAN testers wiki at http://wiki.cpantesters.org/ and the installation guide for CPAN::Reporter at http://wiki.cpantesters.org/wiki/CPANInstall.

Others/todo?

Level 2

    SQLColumnPrivileges
    SQLProcedureColumns
    SQLProcedures
    SQLTablePrivileges
    SQLDrivers
    SQLNativeSql

Random Links

These are in need of sorting and annotating. Some are relevant only to ODBC developers.

You can find DBD::ODBC on ohloh now at:

http://www.ohloh.net/projects/perl_dbd_odbc

If you use ohloh and DBD::ODBC please say you use it and rate it.

There is a good search engine for the various Perl DBI lists at the following URLS:

http://perl.markmail.org/search/list:org.perl.dbi-users

http://perl.markmail.org/search/list:org.perl.dbi-dev

http://perl.markmail.org/search/list:org.perl.dbi-announce

http://www.syware.com

http://www.microsoft.com/odbc

For Linux/Unix folks, compatible ODBC driver managers can be found at:

http://www.unixodbc.org (unixODBC source and rpms)

http://www.iodbc.org (iODBC driver manager source)

For Linux/Unix folks, you can checkout the following for ODBC Drivers and Bridges:

http://www.easysoft.com

http://www.openlinksw.com

http://www.datadirect.com

http://www.atinet.com

Some useful tutorials:

Debugging Perl DBI:

http://www.easysoft.com/developer/languages/perl/dbi-debugging.html

Enabling ODBC support in Perl with Perl DBI and DBD::ODBC:

http://www.easysoft.com/developer/languages/perl/dbi_dbd_odbc.html

Perl DBI/DBD::ODBC Tutorial Part 1 - Drivers, Data Sources and Connection:

http://www.easysoft.com/developer/languages/perl/dbd_odbc_tutorial_part_1.html

Perl DBI/DBD::ODBC Tutorial Part 2 - Introduction to retrieving data from your database:

http://www.easysoft.com/developer/languages/perl/dbd_odbc_tutorial_part_2.html

Perl DBI/DBD::ODBC Tutorial Part 3 - Connecting Perl on UNIX or Linux to Microsoft SQL Server:

http://www.easysoft.com/developer/languages/perl/sql_server_unix_tutorial.html

Perl DBI - Put Your Data On The Web:

http://www.easysoft.com/developer/languages/perl/tutorial_data_web.html

Frequently Asked Questions

Frequently asked questions are now in DBD::ODBC::FAQ. Run perldoc DBD::ODBC::FAQ to view them.

CONFIGURATION AND ENVIRONMENT ^

You should consult the documentation for the ODBC Driver Manager you are using.

DEPENDENCIES ^

DBI

Test::Simple

INCOMPATIBILITIES ^

BUGS AND LIMITATIONS ^

None known other than the deviations from the DBI specification mentioned above in "Deviations from the DBI specification".

Please report any to me via the CPAN RT system. See http://rt.cpan.org/ for more details.

AUTHOR ^

Tim Bunce

Jeff Urlwin

Thomas K. Wenrich

Martin J. Evans

LICENSE AND COPYRIGHT ^

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Portions of this software are Copyright Tim Bunce, Thomas K. Wenrich, Jeff Urlwin and Martin J. Evans - see the source.

SEE ALSO ^

DBI

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