SQL::Parser(3) User Contributed Perl Documentation SQL::Parser(3)NAMESQL::Parser-- validate and parse SQL strings
SYNOPSIS
use SQL::Parser; # CREATE A PARSER OBJECT
my $parser = SQL::Parser->new();
$parser->feature( $class, $name, $value ); # SET OR FIND STATUS OF
my $has_feature = $parser->feature( $class, $name ); # A PARSER FEATURE
$parser->dialect( $dialect_name ); # SET OR FIND STATUS OF
my $current_dialect = $parser->dialect; # A PARSER DIALECT
DESCRIPTIONSQL::Parser is part of the SQL::Statement distribution and, most
interaction with the parser should be done through SQL::Statement. The
methods shown above create and modify a parser object. To use the
parser object to parse SQL and to examine the resulting structure, you
should use SQL::Statement.
Important Note: Previously SQL::Parser had its own hash-based interface
for parsing, but that is now deprecated and will eventually be phased
out in favor of the object-oriented parsing interface of
SQL::Statement. If you are unable to transition some features to the
new interface or have concerns about the phase out, please contact me.
See "The Parse Structure" for details of the now-deprecated hash method
if you still need them.
METHODSnew()
Create a new parser object
use SQL::Parser;
my $parser = SQL::Parser->new();
The new() method creates a SQL::Parser object which can then be used to
parse and validate the syntax of SQL strings. It takes two optional
parameters - 1) the name of the SQL dialect that will define the syntax
rules for the parser and 2) a reference to a hash which can contain
additional attributes of the parser. If no dialect is specified,
'AnyData' is the default.
use SQL::Parser;
my $parser = SQL::Parser->new( $dialect_name, \%attrs );
The dialect_name parameter is a string containing any valid dialect
such as 'ANSI', 'AnyData', or 'CSV'. See the section on the dialect()
method below for details.
The "attrs" parameter is a reference to a hash that can contain error
settings for the PrintError and RaiseError attributes.
An example:
use SQL::Parser;
my $parser = SQL::Parser->new('AnyData', {RaiseError=>1} );
This creates a new parser that uses the grammar rules
contained in the .../SQL/Dialects/AnyData.pm file and which
sets the RaiseError attribute to true.
dialect()
$parser->dialect( $dialect_name ); # load a dialect configuration file
my $dialect = $parser->dialect; # get the name of the current dialect
For example:
$parser->dialect('AnyData'); # loads the AnyData config file
print $parser->dialect; # prints 'AnyData'
The $dialect_name parameter may be the name of any dialect
configuration file on your system. Use the $parser->list('dialects')
method to see a list of available dialects. At a minimum it will
include "ANSI", "CSV", and "AnyData". For backwards compatibility
'Ansi' is accepted as a synonym for 'ANSI', otherwise the names are
case sensitive.
Loading a new dialect configuration file erases all current parser
features and resets them to those defined in the configuration file.
feature()
Features define the rules to be used by a specific parser instance.
They are divided into the following classes:
* valid_commands
* valid_options
* valid_comparison_operators
* valid_data_types
* reserved_words
Within each class a feature name is either enabled or disabled. For
example, under "valid_data_types" the name "BLOB" may be either
disabled or enabled. If it is not enabled (either by being
specifically disabled, or simply by not being specified at all) then
any SQL string using "BLOB" as a data type will throw a syntax error
"Invalid data type: 'BLOB'".
The feature() method allows you to enable, disable, or check the status
of any feature.
$parser->feature( $class, $name, 1 ); # enable a feature
$parser->feature( $class, $name, 0 ); # disable a feature
my $feature = $parser->feature( $class, $name ); # return status of a feature
For example:
$parser->feature('reserved_words','FOO',1); # make 'FOO' a reserved word
$parser->feature('valid_data_types','BLOB',0); # disallow 'BLOB' as a
# data type
# determine if the LIKE
# operator is supported
my $LIKE = $parser->feature('valid_operators','LIKE');
See the section below on "Backwards Compatibility" for use of the
feature() method with SQL::Statement 0.1x style parameters.
Supported SQL syntax
The SQL::Statement distribution can be used to either just parse SQL
statements or to execute them against actual data. A broader set of
syntax is supported in the parser than in the executor. For example
the parser allows you to specify column constraints like PRIMARY KEY.
Currently, these are ignored by the execution engine. Likewise syntax
such as RESTRICT and CASCADE on DROP statements or LOCAL GLOBAL
TEMPORARY tables in CREATE are supported by the parser but ignored by
the executor.
To see the list of Supported SQL syntax formerly kept in this pod, see
SQL::Statement.
Subclassing SQL::Parser
In the event you need to either extend or modify SQL::Parser's default
behavior, the following methods may be overridden:
"$self-">"get_btwn($string)"
Processes the BETWEEN...AND... predicates; default converts to 2
range predicates.
"$self-">"get_in($string)"
Process the IN (...list...) predicates; default converts to a
series of OR'd '=' predicate, or AND'd '<>' predicates for NOT IN.
"$self-">"transform_syntax($string)"
Abstract method; default simply returns the original string.
Called after repl_btwn() and repl_in(), but before any further
predicate processing is applied. Possible uses include converting
other predicate syntax not recognized by SQL::Parser into user-
defined functions.
The parse structure
This section outlines the now-deprecated hash interface to the parsed
structure. It is included for backwards compatibility only. You
should use the SQL::Statement object interface to the structure
instead. See SQL::Statement.
Parse Structures
Here are some further examples of the data structures returned by the
structure() method after a call to parse(). Only specific details are
shown for each SQL instance, not the entire structure.
parse()
Once a SQL::Parser object has been created with the new() method, the
parse() method can be used to parse any number of SQL strings. It
takes a single required parameter -- a string containing a SQL command.
The SQL string may optionally be terminated by a semicolon. The
parse() method returns a true value if the parse is successful and a
false value if the parse finds SQL syntax errors.
Examples:
1) my $success = $parser->parse('SELECT * FROM foo');
2) my $sql = 'SELECT * FROM foo';
my $success = $parser->parse( $sql );
3) my $success = $parser->parse(qq!
SELECT id,phrase
FROM foo
WHERE id < 7
AND phrase <> 'bar'
ORDER BY phrase;
!);
4) my $success = $parser->parse('SELECT * FRoOM foo ');
In examples #1,#2, and #3, the value of $success will be true because
the strings passed to the parse() method are valid SQL strings.
In example #4, however, the value of $success will be false because the
string contains a SQL syntax error ('FRoOM' instead of 'FROM').
In addition to checking the return value of parse() with a variable
like $success, you may use the PrintError and RaiseError attributes as
you would in a DBI script:
* If PrintError is true, then SQL syntax errors will be sent as
warnings to STDERR (i.e. to the screen or to a file if STDERR
has been redirected). This is set to true by default which
means that unless you specifically turn it off, all errors
will be reported.
* If RaiseError is true, then SQL syntax errors will cause the
script to die, (i.e. the script will terminate unless wrapped
in an eval). This is set to false by default which means
that unless you specifically turn it on, scripts will
continue to operate even if there are SQL syntax errors.
Basically, you should leave PrintError on or else you will not be
warned when an error occurs. If you are simply validating a series of
strings, you will want to leave RaiseError off so that the script can
check all strings regardless of whether some of them contain SQL
errors. However, if you are going to try to execute the SQL or need to
depend that it is correct, you should set RaiseError on so that the
program will only continue to operate if all SQL strings use correct
syntax.
IMPORTANT NOTE #1: The parse() method only checks syntax, it does NOT
verify if the objects listed actually exist. For example, given the
string "SELECT model FROM cars", the parse() method will report that
the string contains valid SQL but that will not tell you whether there
actually is a table called "cars" or whether that table contains a
column called 'model'. Those kinds of verifications are performed by
the SQL::Statement module, not by SQL::Parser by itself.
IMPORTANT NOTE #2: The parse() method uses rules as defined by the
selected dialect configuration file and the feature() method. This
means that a statement that is valid in one dialect may not be valid in
another. For example the 'CSV' and 'AnyData' dialects define 'BLOB' as
a valid data type but the 'ANSI' dialect does not. Therefore the
statement 'CREATE TABLE foo (picture BLOB)' would be valid in the first
two dialects but would produce a syntax error in the 'ANSI' dialect.
structure()
After a SQL::Parser object has been created and the parse() method used
to parse a SQL string, the structure() method returns the data
structure of that string. This data structure may be passed on to
other modules (e.g. SQL::Statement) or it may be printed out using, for
example, the Data::Dumper module.
The data structure contains all of the information in the SQL string as
parsed into its various components. To take a simple example:
$parser->parse('SELECT make,model FROM cars');
use Data::Dumper;
print Dumper $parser->structure;
Would produce:
$VAR1 = {
'column_defs' => [
{ 'type' => 'column',
'value' => 'make', },
{ 'type' => 'column',
'value' => 'model', },
],
'command' => 'SELECT',
'table_names' => [
'cars'
]
};
'SELECT make,model, FROM cars'
command => 'SELECT',
table_names => [ 'cars' ],
column_names => [ 'make', 'model' ],
'CREATE TABLE cars ( id INTEGER, model VARCHAR(40) )'
column_defs => {
id => { data_type => INTEGER },
model => { data_type => VARCHAR(40) },
},
'SELECT DISTINCT make FROM cars'
set_quantifier => 'DISTINCT',
'SELECT MAX (model) FROM cars'
set_function => {
name => 'MAX',
arg => 'models',
},
'SELECT * FROM cars LIMIT 5,10'
limit_clause => {
offset => 5,
limit => 10,
},
'SELECT * FROM vars ORDER BY make, model DESC'
sort_spec_list => [
{ make => 'ASC' },
{ model => 'DESC' },
],
"INSERT INTO cars VALUES ( 7, 'Chevy', 'Impala' )"
values => [ 7, 'Chevy', 'Impala' ],
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc SQL::Parser
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>
· Search CPAN
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 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 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.
AUTHOR & COPYRIGHT
This module is
copyright (c) 2001,2005 by Jeff Zucker and
copyright (c) 2008,2010 by Jens Rehsack.
All rights reserved.
The module may be freely distributed under the same terms as Perl
itself using either the "GPL License" or the "Artistic License" as
specified in the Perl README file.
Jeff can be reached at: jzuckerATcpan.org Jens can be reached at:
rehsackATcpan.org or via dbi-devATperl.org
perl v5.14.1 2011-02-01 SQL::Parser(3)
