SQL::Statement(3) User Contributed Perl Documentation SQL::Statement(3)NAMESQL::Statement - SQL parsing and processing engine
SYNOPSIS
# ... depends on what you want to do, see below
DESCRIPTION
The SQL::Statement module implements a pure Perl SQL parsing and
execution engine. While it by no means implements full ANSI standard,
it does support many features including column and table aliases,
built-in and user-defined functions, implicit and explicit joins,
complex nested search conditions, and other features.
SQL::Statement is a small embeddable Database Management System (DBMS).
This means that it provides all of the services of a simple DBMS except
that instead of a persistent storage mechanism, it has two things: 1)
an in-memory storage mechanism that allows you to prepare, execute, and
fetch from SQL statements using temporary tables and 2) a set of
software sockets where any author can plug in any storage mechanism.
There are three main uses for SQL::Statement. One or another (hopefully
not all) may be irrelevant for your needs: 1) to access and manipulate
data in CSV, XML, and other formats 2) to build your own DBD for a new
data source 3) to parse and examine the structure of SQL statements.
INSTALLATION
There are no prerequisites for using this as a standalone parser. If
you want to access persistent stored data, you either need to write a
subclass or use one of the DBI DBD drivers. You can install this
module using CPAN.pm, CPANPLUS.pm, PPM, apt-get, or other packaging
tools or you can download the tar.gz file from CPAN and use the
standard perl mantra:
perl Makefile.PL
make
make test
make install
It works fine on all platforms it has been tested on. On Windows, you
can use ppm or with the mantra use nmake, dmake, or make depending on
which is available.
USAGE
How can I use SQL::Statement to access and modify data?
SQL::Statement provides the SQL engine for a number of existing DBI
drivers including DBD::CSV, DBD::DBM, DBD::AnyData, DBD::Excel,
DBD::Amazon, and others.
These modules provide access to Comma Separated Values, Fixed Length,
XML, HTML and many other kinds of text files, to Excel Spreadsheets, to
BerkeleyDB and other DBM formats, and to non-traditional data sources
like on-the-fly Amazon searches.
If you are interested in accessing and manipulating persistent data,
you may not really want to use SQL::Statement directly, but use DBI
along with one of the DBDs mentioned above instead. You will be using
SQL::Statement, but under the hood of the DBD. See
<http://dbi.perl.org> for help with DBI and see SQL::Statement::Syntax
for a description of the SQL syntax that SQL::Statement provides for
these modules and see the documentation for whichever DBD you are using
for additional details.
How can I use it to parse and examine the structure of SQL statements?
SQL::Statement can be used stand-alone (without a subclass and without
DBI) to parse and examine the structure of SQL statements. See
SQL::Statement::Structure for details.
How can I use it to embed a SQL engine in a DBD or other module?
SQL::Statement is designed to be easily embedded in other modules and
is especially suited for developing new DBI drivers (DBDs). See
SQL::Statement::Embed.
What SQL Syntax is supported?
SQL::Statement supports a small but powerful subset of SQL commands.
See SQL::Statement::Syntax.
How can I extend the supported SQL syntax?
You can modify and extend the SQL syntax either by issuing SQL commands
or by subclassing SQL::Statement. See SQL::Statement::Syntax.
How can I participate in ongoing development?
SQL::Statement is a large module with many potential future directions.
You are invited to help plan, code, test, document, or kibbitz about
these directions. If you want to join the development team, or just
hear more about the development, write Jeff (<jzuckerATcpan.org>) or
Jens (<rehsackATcpan.org>) a note.
METHODS
The following methods can or must be overridden by derived classes.
capability
$has_capability = $h->capability('capability_name');
Returns a true value if the specified capability is available.
Currently no capabilities are defined and this is a placeholder for
future use. It is envisioned it will be used like
"SQL::Eval::Table::capability".
open_table
The "open_table" method must be overridden by derived classes to
provide the capability of opening data tables. This is a necessity.
Arguments given to open_table call:
$data
The database memo parameter. See "execute".
$table
The name of the table to open as parsed from SQL statement.
$createMode
A flag indicating the mode ("CREATE TABLE ...") the table should be
opened with. Set to a true value in create mode.
$lockMode
A flag indicating whether the table should be opened for writing
(any other than "SELECT ..."). Set to a true value if the table is
to be opened for write access.
The following methods are required to use SQL::Statement in a DBD (for
example).
new
Instantiates a new SQL::Statement object.
Arguments:
$sql
The SQL statement for later actions.
$parser
An instance of a SQL::Parser object or flags for it's
instantiation. If omitted, default flags are used.
When the basic initialization is completed, "$self->prepare($sql,
$parser)" is invoked.
prepare
Prepares SQL::Statement to execute a SQL statement.
Arguments:
$sql
The SQL statement to parse and prepare.
$parser
Instance of a SQL::Parser object to parse the provided SQL
statement.
execute
Executes a prepared statement.
Arguments:
$data
Memo field passed through to calls of the instantiated $table
objects or "open_table" calls. In "CREATE" with subquery,
"$data->{Database}" must be a DBI database handle object.
$params
Bound params via DBI ...
errstr
Gives the error string of the last error, if any.
fetch_row
Fetches the next row from the result data set (implies removing the
fetched row from the result data set).
fetch_rows
Fetches all (remaining) rows from the result data set.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc SQL::Statement
You can also look for information at:
· RT: CPAN's request tracker
http://rt.cpan.org/NoAuth/Bugs.html?Dist=SQL-Statement
<http://rt.cpan.org/NoAuth/Bugs.html?Dist=SQL-Statement>
· AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/SQL-Statement
<http://annocpan.org/dist/SQL-Statement>
· CPAN Ratings
http://cpanratings.perl.org/s/SQL-Statement
<http://cpanratings.perl.org/s/SQL-Statement>
· CPAN Search
http://search.cpan.org/dist/SQL-Statement/
<http://search.cpan.org/dist/SQL-Statement/>
Where can I go for help?
For questions about installation or usage, please ask on the
dbi-users@perl.org mailing list (see http://dbi.perl.org) or post a
question on PerlMonks (<http://www.perlmonks.org/>, where Jeff is known
as jZed). Jens does not visit PerlMonks on a regular basis.
If you have a bug report, a patch or a suggestion, please open a new
report ticket at CPAN (but please check previous reports first in case
your issue has already been addressed). You can mail any of the module
maintainers, but you are more assured of an answer by posting to the
dbi-users list or reporting the issue in RT.
Report tickets should contain a detailed description of the bug or
enhancement request and at least an easily verifiable way of
reproducing the issue or fix. Patches are always welcome, too.
Where can I go for help with a concrete version?
Bugs and feature requests are accepted against the latest version only.
To get patches for earlier versions, you need to get an agreement with
a developer of your choice - who may or not report the issue and a
suggested fix upstream (depends on the license you have chosen).
Business support and maintenance
For business support you can contact Jens via his CPAN email address
rehsackATcpan.org. Please keep in mind that business support is neither
available for free nor are you eligible to receive any support based on
the license distributed with this package.
ACKNOWLEDGEMENTS
Jochen Wiedmann created the original module as an XS (C) extension in
1998. Jeff Zucker took over the maintenance in 2001 and rewrote all of
the C portions in Perl and began extending the SQL support. More
recently Ilya Sterin provided help with SQL::Parser, Tim Bunce provided
both general and specific support, Dan Wright and Dean Arnold have
contributed extensively to the code, and dozens of people from around
the world have submitted patches, bug reports, and suggestions.
In 2008 Jens Rehsack took over the maintenance of the extended module
from Jeff. Together with H.Merijn Brand (who has taken DBD::CSV),
Detlef Wartke and Volker Schubbert (especially between 1.16 developer
versions until 1.22) and all submitters of bug reports via RT a lot of
issues have been fixed.
Thanks to all!
If you're interested in helping develop SQL::Statement or want to use
it with your own modules, feel free to contact Jeff or Jens.
BUGS AND LIMITATIONS
· Currently we treat NULL and '' as the same in AnyData/CSV mode -
eventually fix.
· No nested C-style comments allowed as SQL99 says.
· There are some issues regarding combining outer joins with where
clauses.
· Aggregate functions cannot be used in where clause.
· Some SQL commands/features are not supported (most of them cannot
by design), as "LOCK TABLE", using indices, sub-selects etc.
Currently the statement for missing features is: I plan to create a
SQL::Statement v2.00 based on a pure Backus-Naur-Form parser and a
fully object oriented command pattern based engine implementation.
When the time is available, I will do it. Until then bugs will be
fixed or other Perl modules under my maintainership will receive my
time. Features which can be added without deep design changes might
be applied earlier - especially when their addition allows studying
effective ways to implement the feature in upcoming 2.00.
· Some people report that SQL::Statement is slower since the XS parts
were implemented in pure Perl. This might be true, but on the other
hand a large number of features have been added including support
for ANSI SQL 99.
For SQL::Statement 1.xx it's not planned to add new XS parts.
· Wildcards are expanded to lower cased identifiers. This might
confuse some people, but it was easier to implement.
The warning in DBI to never trust the case of returned column names
should be read more often. If you need to rely on identifiers,
always use "sth->{NAME_lc}" or "sth->{NAME_uc}" - never rely on
"sth->{NAME}":
$dbh->{FetchHashKeyName} = 'NAME_lc';
$sth = $dbh->prepare("SELECT FOO, BAR, ID, NAME, BAZ FROM TABLE");
$sth->execute;
$hash_ref = $sth->fetchall_hashref('id');
print "Name for id 42 is $hash_ref->{42}->{name}\n";
See "FetchHashKeyName" in DBI for more information.
· Unable to use the same table twice with different aliases.
Workaround: Temporary tables: "CREATE TEMP TABLE t_foo AS SELECT *
FROM foo". Than both tables can be used independently.
Patches to fix bugs/limitations (or a grant to do it) would be very
welcome. Please note, that any patches must successfully pass all the
"SQL::Statement", DBD::File and DBD::CSV tests and must be a general
improvement.
AUTHOR AND COPYRIGHT
Jochen Wiedmann created the original module as an XS (C) extension in
1998. Jeff Zucker took over the maintenance in 2001 and rewrote all of
the C portions in perl and began extending the SQL support. Since 2008,
Jens Rehsack is the maintainer.
Copyright (c) 2001,2005 by Jeff Zucker: jzuckerATcpan.org Copyright (c)
2007-2010 by Jens Rehsack: rehsackATcpan.org
Portions Copyright (C) 1998 by Jochen Wiedmann: jwiedATcpan.org
All rights reserved.
You may distribute this module under the terms of either the GNU
General Public License or the Artistic License, as specified in the
Perl README file.
perl v5.14.1 2011-02-01 SQL::Statement(3)
