package SQL::Abstract; # see doc at end of file
-# LDNOTE : this code is heavy refactoring from original SQLA.
-# Several design decisions will need discussion during
-# the test / diffusion / acceptance phase; those are marked with flag
-# 'LDNOTE' (note by laurent.dami AT free.fr)
-
use strict;
use warnings;
use Carp ();
use List::Util ();
use Scalar::Util ();
+use Exporter 'import';
+our @EXPORT_OK = qw(is_plain_value is_literal_value);
+
+BEGIN {
+ if ($] < 5.009_005) {
+ require MRO::Compat;
+ }
+ else {
+ require mro;
+ }
+}
+
#======================================================================
# GLOBALS
#======================================================================
-our $VERSION = '1.72';
+our $VERSION = '1.78';
# This would confuse some packagers
$VERSION = eval $VERSION if $VERSION =~ /_/; # numify for warning-free dev releases
my @BUILTIN_SPECIAL_OPS = (
{regex => qr/^ (?: not \s )? between $/ix, handler => '_where_field_BETWEEN'},
{regex => qr/^ (?: not \s )? in $/ix, handler => '_where_field_IN'},
+ {regex => qr/^ ident $/ix, handler => '_where_op_IDENT'},
+ {regex => qr/^ value $/ix, handler => '_where_op_VALUE'},
+ {regex => qr/^ is (?: \s+ not )? $/ix, handler => '_where_field_IS'},
);
# unaryish operators - key maps to handler
{ regex => qr/^ or (?: [_\s]? \d+ )? $/xi, handler => '_where_op_ANDOR' },
{ regex => qr/^ nest (?: [_\s]? \d+ )? $/xi, handler => '_where_op_NEST' },
{ regex => qr/^ (?: not \s )? bool $/xi, handler => '_where_op_BOOL' },
+ { regex => qr/^ ident $/xi, handler => '_where_op_IDENT' },
+ { regex => qr/^ value $/xi, handler => '_where_op_VALUE' },
);
#======================================================================
Carp::croak "[$func] Fatal: ", @_;
}
+sub is_literal_value ($) {
+ ref $_[0] eq 'SCALAR' ? [ ${$_[0]} ]
+ : ( ref $_[0] eq 'REF' and ref ${$_[0]} eq 'ARRAY' ) ? [ @${ $_[0] } ]
+ : (
+ ref $_[0] eq 'HASH' and keys %{$_[0]} == 1
+ and
+ defined $_[0]->{-ident} and ! length ref $_[0]->{-ident}
+ ) ? [ $_[0]->{-ident} ]
+ : undef;
+}
+
+# FIXME XSify - this can be done so much more efficiently
+sub is_plain_value ($) {
+ no strict 'refs';
+ ! length ref $_[0] ? [ $_[0] ]
+ : (
+ ref $_[0] eq 'HASH' and keys %{$_[0]} == 1
+ and
+ exists $_[0]->{-value}
+ ) ? [ $_[0]->{-value} ]
+ : (
+ Scalar::Util::blessed $_[0]
+ and
+ # deliberately not using Devel::OverloadInfo - the checks we are
+ # intersted in are much more limited than the fullblown thing, and
+ # this is a very hot piece of code
+ (
+ # FIXME - DBI needs fixing to stringify regardless of DBD
+ #
+ # FIXME - simply using ->can('(""') trips up Path::Class in
+ # inexplicable ways under -T (likely other modules too)
+ #
+ # either has stringification which DBI SHOULD prefer out of the box
+ grep { *{ (qq[${_}::(""]) }{CODE} } @{ mro::get_linear_isa( ref $_[0] ) }
+ or
+ # has nummification and fallback is *not* disabled
+ # reuse @_ for even moar speedz
+ (
+ # FIXME - simply using ->can('(0+') trips up Path::Class in
+ # inexplicable ways under -T (likely other modules too)
+ grep { *{"${_}::(0+"}{CODE} } @{ mro::get_linear_isa( ref $_[0] ) }
+ and
+ (
+ # no fallback specified at all
+ ! ( ($_[1]) = grep { *{"${_}::()"}{CODE} } @{ mro::get_linear_isa( ref $_[0] ) } )
+ or
+ # fallback explicitly undef
+ ! defined ${"$_[1]::()"}
+ or
+ # explicitly true
+ ${"$_[1]::()"}
+ )
+ )
+ )
+ ) ? [ "$_[0]" ]
+ : undef;
+}
+
+
#======================================================================
# NEW
$opt{logic} = $opt{logic} ? uc $opt{logic} : 'OR';
# how to return bind vars
- # LDNOTE: changed nwiger code : why this 'delete' ??
- # $opt{bindtype} ||= delete($opt{bind_type}) || 'normal';
$opt{bindtype} ||= 'normal';
# default comparison is "=", but can be overridden
$opt{cmp} ||= '=';
- # try to recognize which are the 'equality' and 'unequality' ops
- # (temporary quickfix, should go through a more seasoned API)
- $opt{equality_op} = qr/^(\Q$opt{cmp}\E|is|(is\s+)?like)$/i;
- $opt{inequality_op} = qr/^(!=|<>|(is\s+)?not(\s+like)?)$/i;
+ # try to recognize which are the 'equality' and 'inequality' ops
+ # (temporary quickfix (in 2007), should go through a more seasoned API)
+ $opt{equality_op} = qr/^( \Q$opt{cmp}\E | \= )$/ix;
+ $opt{inequality_op} = qr/^( != | <> )$/ix;
+
+ $opt{like_op} = qr/^ (is\s+)? r?like $/xi;
+ $opt{not_like_op} = qr/^ (is\s+)? not \s+ r?like $/xi;
# SQL booleans
$opt{sqltrue} ||= '1=1';
$opt{unary_ops} ||= [];
push @{$opt{unary_ops}}, @BUILTIN_UNARY_OPS;
- # rudimentary saniy-check for user supplied bits treated as functions/operators
+ # rudimentary sanity-check for user supplied bits treated as functions/operators
# If a purported function matches this regular expression, an exception is thrown.
# Literal SQL is *NOT* subject to this check, only functions (and column names
# when quoting is not in effect)
},
HASHREF => sub {$self->_recurse_where($el, 'and') if %$el},
- # LDNOTE : previous SQLA code for hashrefs was creating a dirty
- # side-effect: the first hashref within an array would change
- # the global logic to 'AND'. So [ {cond1, cond2}, [cond3, cond4] ]
- # was interpreted as "(cond1 AND cond2) OR (cond3 AND cond4)",
- # whereas it should be "(cond1 AND cond2) OR (cond3 OR cond4)".
SCALARREF => sub { ($$el); },
}
+sub _where_op_IDENT {
+ my $self = shift;
+ my ($op, $rhs) = splice @_, -2;
+ if (ref $rhs) {
+ puke "-$op takes a single scalar argument (a quotable identifier)";
+ }
+
+ # in case we are called as a top level special op (no '=')
+ my $lhs = shift;
+
+ $_ = $self->_convert($self->_quote($_)) for ($lhs, $rhs);
+
+ return $lhs
+ ? "$lhs = $rhs"
+ : $rhs
+ ;
+}
+
+sub _where_op_VALUE {
+ my $self = shift;
+ my ($op, $rhs) = splice @_, -2;
+
+ # in case we are called as a top level special op (no '=')
+ my $lhs = shift;
+
+ # special-case NULL
+ if (! defined $rhs) {
+ return $lhs
+ ? $self->_convert($self->_quote($lhs)) . ' IS NULL'
+ : undef
+ ;
+ }
+
+ my @bind =
+ $self->_bindtype (
+ ($lhs || $self->{_nested_func_lhs}),
+ $rhs,
+ )
+ ;
+
+ return $lhs
+ ? (
+ $self->_convert($self->_quote($lhs)) . ' = ' . $self->_convert('?'),
+ @bind
+ )
+ : (
+ $self->_convert('?'),
+ @bind,
+ )
+ ;
+}
+
sub _where_hashpair_ARRAYREF {
my ($self, $k, $v) = @_;
return $self->_recurse_where(\@distributed, $logic);
}
else {
- # LDNOTE : not sure of this one. What does "distribute over nothing" mean?
$self->_debug("empty ARRAY($k) means 0=1");
return ($self->{sqlfalse});
}
$self->_assert_pass_injection_guard($op);
+ # fixup is_not
+ $op =~ s/^is_not/IS NOT/i;
+
# so that -not_foo works correctly
$op =~ s/^not_/NOT /i;
+ # another retarded special case: foo => { $op => { -value => undef } }
+ if (ref $val eq 'HASH' and keys %$val == 1 and exists $val->{-value} and ! defined $val->{-value} ) {
+ $val = undef;
+ }
+
my ($sql, @bind);
# CASE: col-value logic modifiers
},
UNDEF => sub { # CASE: col => {op => undef} : sql "IS (NOT)? NULL"
- my $is = ($op =~ $self->{equality_op}) ? 'is' :
- ($op =~ $self->{inequality_op}) ? 'is not' :
- puke "unexpected operator '$orig_op' with undef operand";
+ my $is =
+ $op =~ /^not$/i ? 'is not' # legacy
+ : $op =~ $self->{equality_op} ? 'is'
+ : $op =~ $self->{like_op} ? belch("Supplying an undefined argument to '@{[ uc $op]}' is deprecated") && 'is'
+ : $op =~ $self->{inequality_op} ? 'is not'
+ : $op =~ $self->{not_like_op} ? belch("Supplying an undefined argument to '@{[ uc $op]}' is deprecated") && 'is not'
+ : puke "unexpected operator '$orig_op' with undef operand";
+
$sql = $self->_quote($k) . $self->_sqlcase(" $is null");
},
return ($all_sql, @all_bind);
}
+sub _where_field_IS {
+ my ($self, $k, $op, $v) = @_;
+
+ my ($s) = $self->_SWITCH_refkind($v, {
+ UNDEF => sub {
+ join ' ',
+ $self->_convert($self->_quote($k)),
+ map { $self->_sqlcase($_)} ($op, 'null')
+ },
+ FALLBACK => sub {
+ puke "$op can only take undef as argument";
+ },
+ });
+ $s;
+}
sub _where_field_op_ARRAYREF {
my ($self, $k, $op, $vals) = @_;
shift @vals;
}
+ # a long standing API wart - an attempt to change this behavior during
+ # the 1.50 series failed *spectacularly*. Warn instead and leave the
+ # behavior as is
+ if (
+ @vals > 1
+ and
+ (!$logic or $logic eq 'OR')
+ and
+ ( $op =~ $self->{inequality_op} or $op =~ $self->{not_like_op} )
+ ) {
+ my $o = uc($op);
+ belch "A multi-element arrayref as an argument to the inequality op '$o' "
+ . 'is technically equivalent to an always-true 1=1 (you probably wanted '
+ . "to say ...{ \$inequality_op => [ -and => \@values ] }... instead)"
+ ;
+ }
+
# distribute $op over each remaining member of @vals, append logic if exists
return $self->_recurse_where([map { {$k => {$op, $_}} } @vals], $logic);
- # LDNOTE : had planned to change the distribution logic when
- # $op =~ $self->{inequality_op}, because of Morgan laws :
- # with {field => {'!=' => [22, 33]}}, it would be ridiculous to generate
- # WHERE field != 22 OR field != 33 : the user probably means
- # WHERE field != 22 AND field != 33.
- # To do this, replace the above to roughly :
- # my $logic = ($op =~ $self->{inequality_op}) ? 'AND' : 'OR';
- # return $self->_recurse_where([map { {$k => {$op, $_}} } @vals], $logic);
-
}
else {
# try to DWIM on equality operators
- # LDNOTE : not 100% sure this is the correct thing to do ...
- return ($self->{sqlfalse}) if $op =~ $self->{equality_op};
- return ($self->{sqltrue}) if $op =~ $self->{inequality_op};
-
- # otherwise
- puke "operator '$op' applied on an empty array (field '$k')";
+ return
+ $op =~ $self->{equality_op} ? $self->{sqlfalse}
+ : $op =~ $self->{like_op} ? belch("Supplying an empty arrayref to '@{[ uc $op]}' is deprecated") && $self->{sqlfalse}
+ : $op =~ $self->{inequality_op} ? $self->{sqltrue}
+ : $op =~ $self->{not_like_op} ? belch("Supplying an empty arrayref to '@{[ uc $op]}' is deprecated") && $self->{sqltrue}
+ : puke "operator '$op' applied on an empty array (field '$k')";
}
}
$placeholder = $self->_convert('?');
$op = $self->_sqlcase($op);
+ my $invalid_args = "Operator '$op' requires either an arrayref with two defined values or expressions, or a single literal scalarref/arrayref-ref";
+
my ($clause, @bind) = $self->_SWITCH_refkind($vals, {
ARRAYREFREF => sub {
my ($s, @b) = @$$vals;
return $$vals;
},
ARRAYREF => sub {
- puke "special op 'between' accepts an arrayref with exactly two values"
- if @$vals != 2;
+ puke $invalid_args if @$vals != 2;
my (@all_sql, @all_bind);
foreach my $val (@$vals) {
if (@rest or $func !~ /^ \- (.+)/x);
local $self->{_nested_func_lhs} = $k;
$self->_where_unary_op ($1 => $arg);
- }
+ },
+ FALLBACK => sub {
+ puke $invalid_args,
+ },
});
push @all_sql, $sql;
push @all_bind, @bind;
);
},
FALLBACK => sub {
- puke "special op 'between' accepts an arrayref with two values, or a single literal scalarref/arrayref-ref";
+ puke $invalid_args,
},
});
$self->_where_unary_op ($1 => $arg);
},
UNDEF => sub {
- return $self->_sqlcase('null');
+ puke(
+ 'SQL::Abstract before v1.75 used to generate incorrect SQL when the '
+ . "-$op operator was given an undef-containing list: !!!AUDIT YOUR CODE "
+ . 'AND DATA!!! (the upcoming Data::Query-based version of SQL::Abstract '
+ . 'will emit the logically correct SQL instead of raising this exception)'
+ );
},
});
push @all_sql, $sql;
return ("$label $op ( $sql )", @bind);
},
+ UNDEF => sub {
+ puke "Argument passed to the '$op' operator can not be undefined";
+ },
+
FALLBACK => sub {
- puke "special op 'in' requires an arrayref (or scalarref/arrayref-ref)";
+ puke "special op $op requires an arrayref (or scalarref/arrayref-ref)";
},
});
else {
puke "Unsupported quote_char format: $_[0]->{quote_char}";
}
+ my $esc = $_[0]->{escape_char} || $r;
# parts containing * are naturally unquoted
return join( $_[0]->{name_sep}||'', map
- { $_ eq '*' ? $_ : $l . $_ . $r }
+ { $_ eq '*' ? $_ : do { (my $n = $_) =~ s/(\Q$esc\E|\Q$r\E)/$esc$1/g; $l . $n . $r } }
( $_[0]->{name_sep} ? split (/\Q$_[0]->{name_sep}\E/, $_[1] ) : $_[1] )
);
}
# Conversion, if applicable
sub _convert ($) {
#my ($self, $arg) = @_;
-
-# LDNOTE : modified the previous implementation below because
-# it was not consistent : the first "return" is always an array,
-# the second "return" is context-dependent. Anyway, _convert
-# seems always used with just a single argument, so make it a
-# scalar function.
-# return @_ unless $self->{convert};
-# my $conv = $self->_sqlcase($self->{convert});
-# my @ret = map { $conv.'('.$_.')' } @_;
-# return wantarray ? @ret : $ret[0];
if ($_[0]->{convert}) {
return $_[0]->_sqlcase($_[0]->{convert}) .'(' . $_[1] . ')';
}
# And bindtype
sub _bindtype (@) {
#my ($self, $col, @vals) = @_;
-
- #LDNOTE : changed original implementation below because it did not make
- # sense when bindtype eq 'columns' and @vals > 1.
-# return $self->{bindtype} eq 'columns' ? [ $col, @vals ] : @vals;
-
# called often - tighten code
return $_[0]->{bindtype} eq 'columns'
? map {[$_[1], $_]} @_[2 .. $#_]
my $sql = SQL::Abstract->new;
- my($stmt, @bind) = $sql->select($table, \@fields, \%where, \@order);
+ my($stmt, @bind) = $sql->select($source, \@fields, \%where, \@order);
my($stmt, @bind) = $sql->insert($table, \%fieldvals || \@values);
Easy, eh?
-=head1 FUNCTIONS
+=head1 METHODS
-The functions are simple. There's one for each major SQL operation,
+The methods are simple. There's one for each major SQL operation,
and a constructor you use first. The arguments are specified in a
-similar order to each function (table, then fields, then a where
+similar order to each method (table, then fields, then a where
clause) to try and simplify things.
-
-
-
=head2 new(option => 'value')
The C<new()> function takes a list of options and values, and returns
WHERE name like 'nwiger' AND email like 'nate@wiger.org'
-You can also override the comparsion on an individual basis - see
+You can also override the comparison on an individual basis - see
the huge section on L</"WHERE CLAUSES"> at the bottom.
=item sqltrue, sqlfalse
Quoting is useful if you have tables or columns names that are reserved
words in your database's SQL dialect.
+=item escape_char
+
+This is the character that will be used to escape L</quote_char>s appearing
+in an identifier before it has been quoted.
+
+The paramter default in case of a single L</quote_char> character is the quote
+character itself.
+
+When opening-closing-style quoting is used (L</quote_char> is an arrayref)
+this parameter defaults to the B<closing (right)> L</quote_char>. Occurences
+of the B<opening (left)> L</quote_char> within the identifier are currently left
+untouched. The default for opening-closing-style quotes may change in future
+versions, thus you are B<strongly encouraged> to specify the escape character
+explicitly.
+
=item name_sep
This is the character that separates a table and column name. It is
The argument can be either an arrayref (interpreted as a list
of field names, will be joined by commas and quoted), or a
plain scalar (literal SQL, not quoted).
-Please observe that this API is not as flexible as for
-the first argument C<$table>, for backwards compatibility reasons.
+Please observe that this API is not as flexible as that of
+the first argument C<$source>, for backwards compatibility reasons.
=item $where
You get the idea. Strings get their case twiddled, but everything
else remains verbatim.
+=head1 EXPORTABLE FUNCTIONS
+
+=head2 is_plain_value
+
+Determines if the supplied argument is a plain value as understood by this
+module:
+
+=over
+
+=item * The value is C<undef>
+
+=item * The value is a non-reference
+
+=item * The value is an object with stringification overloading
+
+=item * The value is of the form C<< { -value => $anything } >>
+
+=back
+
+On failure returns C<undef>, on sucess returns a reference to a single
+element array containing the string-version of the supplied argument or
+C<[ undef ]> in case of an undefined initial argument.
+
+=head2 is_literal_value
+
+Determines if the supplied argument is a literal value as understood by this
+module:
+
+=over
+
+=item * C<\$sql_string>
+=item * C<\[ $sql_string, @bind_values ]>
+=item * C<< { -ident => $plain_defined_string } >>
+
+=back
+
+On failure returns C<undef>, on sucess returns a reference to an array
+cotaining the unpacked version of the supplied literal SQL and bind values.
=head1 WHERE CLAUSES
user => 'nwiger',
status => { '!=', undef },
);
-
+
=head2 Specific comparison operators
If you want to specify a different type of operator for your comparison,
)";
@bind = ('2000');
-
+Finally, if the argument to C<-in> is not a reference, it will be
+treated as a single-element array.
Another pair of operators is C<-between> and C<-not_between>,
used with an arrayref of two values:
my %where = (
-and => [
-bool => 'one',
- -bool => 'two',
- -bool => 'three',
- -not_bool => 'four',
+ -not_bool => { two=> { -rlike => 'bar' } },
+ -not_bool => { three => [ { '=', 2 }, { '>', 5 } ] },
],
);
Would give you:
- WHERE one AND two AND three AND NOT four
+ WHERE
+ one
+ AND
+ (NOT two RLIKE ?)
+ AND
+ (NOT ( three = ? OR three > ? ))
=head2 Nested conditions, -and/-or prefixes
OR ( workhrs < ? OR geo = ? )
) )
-=head2 Algebraic inconsistency, for historical reasons
+=head3 Algebraic inconsistency, for historical reasons
C<Important note>: when connecting several conditions, the C<-and->|C<-or>
operator goes C<outside> of the nested structure; whereas when connecting
# yields : WHERE ( ( col LIKE ? OR col LIKE ? ) )
-=head2 Literal SQL
+=head2 Literal SQL and value type operators
+
+The basic premise of SQL::Abstract is that in WHERE specifications the "left
+side" is a column name and the "right side" is a value (normally rendered as
+a placeholder). This holds true for both hashrefs and arrayref pairs as you
+see in the L</WHERE CLAUSES> examples above. Sometimes it is necessary to
+alter this behavior. There are several ways of doing so.
-Finally, sometimes only literal SQL will do.
-To include literal SQL verbatim, you specify it as a scalar reference.
-Consider this only as a last resort. Usually there is a better way.
+=head3 -ident
-Literal SQL is the only way to compare 2 columns to one another:
+This is a virtual operator that signals the string to its right side is an
+identifier (a column name) and not a value. For example to compare two
+columns you would write:
my %where = (
priority => { '<', 2 },
- requestor => \'= submittor'
+ requestor => { -ident => 'submitter' },
);
which creates:
$stmt = "WHERE priority < ? AND requestor = submitter";
@bind = ('2');
+If you are maintaining legacy code you may see a different construct as
+described in L</Deprecated usage of Literal SQL>, please use C<-ident> in new
+code.
-There is a nicer way to test for NULL, but just for the sake of example:
+=head3 -value
+
+This is a virtual operator that signals that the construct to its right side
+is a value to be passed to DBI. This is for example necessary when you want
+to write a where clause against an array (for RDBMS that support such
+datatypes). For example:
- my $inn = 'IS NOT NULL';
my %where = (
- priority => { '<', 2 },
- requestor => \$inn
+ array => { -value => [1, 2, 3] }
);
-This would create:
-
- $stmt = "WHERE priority < ? AND requestor is Not Null";
- @bind = ('2');
+will result in:
-Note that in this example, you only get one bind parameter back, since
-the verbatim SQL is passed as part of the statement.
+ $stmt = 'WHERE array = ?';
+ @bind = ([1, 2, 3]);
-Of course, just to prove a point, the above can also be accomplished
-with this:
+Note that if you were to simply say:
my %where = (
- priority => { '<', 2 },
- requestor => { '!=', undef },
+ array => [1, 2, 3]
);
+the result would probably not be what you wanted:
+
+ $stmt = 'WHERE array = ? OR array = ? OR array = ?';
+ @bind = (1, 2, 3);
-Conditions on boolean columns can be expressed by passing
-a reference to an empty string, however using liternal SQL in this way
-is deprecated - the preferred method is to use the boolean operators -
-see L</"Unary operators: bool"> :
+=head3 Literal SQL
+
+Finally, sometimes only literal SQL will do. To include a random snippet
+of SQL verbatim, you specify it as a scalar reference. Consider this only
+as a last resort. Usually there is a better way. For example:
my %where = (
- priority => { '<', 2 },
- is_ready => \"";
+ priority => { '<', 2 },
+ requestor => { -in => \'(SELECT name FROM hitmen)' },
);
-which yields
+Would create:
- $stmt = "WHERE priority < ? AND is_ready";
- @bind = ('2');
+ $stmt = "WHERE priority < ? AND requestor IN (SELECT name FROM hitmen)"
+ @bind = (2);
+
+Note that in this example, you only get one bind parameter back, since
+the verbatim SQL is passed as part of the statement.
+
+=head4 CAVEAT
-=head2 Literal SQL with placeholders and bind values (subqueries)
+ Never use untrusted input as a literal SQL argument - this is a massive
+ security risk (there is no way to check literal snippets for SQL
+ injections and other nastyness). If you need to deal with untrusted input
+ use literal SQL with placeholders as described next.
+
+=head3 Literal SQL with placeholders and bind values (subqueries)
If the literal SQL to be inserted has placeholders and bind values,
use a reference to an arrayref (yes this is a double reference --
$stmt = "lname LIKE ? AND NOT ( age < ? OR age > ? )"
@bind = ('%son%', 10, 20)
+=head3 Deprecated usage of Literal SQL
+
+Below are some examples of archaic use of literal SQL. It is shown only as
+reference for those who deal with legacy code. Each example has a much
+better, cleaner and safer alternative that users should opt for in new code.
+
+=over
+
+=item *
+
+ my %where = ( requestor => \'IS NOT NULL' )
+
+ $stmt = "WHERE requestor IS NOT NULL"
+
+This used to be the way of generating NULL comparisons, before the handling
+of C<undef> got formalized. For new code please use the superior syntax as
+described in L</Tests for NULL values>.
+
+=item *
+
+ my %where = ( requestor => \'= submitter' )
+
+ $stmt = "WHERE requestor = submitter"
+
+This used to be the only way to compare columns. Use the superior L</-ident>
+method for all new code. For example an identifier declared in such a way
+will be properly quoted if L</quote_char> is properly set, while the legacy
+form will remain as supplied.
+
+=item *
+
+ my %where = ( is_ready => \"", completed => { '>', '2012-12-21' } )
+
+ $stmt = "WHERE completed > ? AND is_ready"
+ @bind = ('2012-12-21')
+Using an empty string literal used to be the only way to express a boolean.
+For all new code please use the much more readable
+L<-bool|/Unary operators: bool> operator.
+
+=back
=head2 Conclusion
dynamically-generating SQL and could just hardwire it into your
script.
-
-
-
=head1 ORDER BY CLAUSES
Some functions take an order by clause. This can either be a scalar (just a
#!/usr/bin/perl
+ use warnings;
+ use strict;
+
use CGI::FormBuilder;
use SQL::Abstract;
=back
-
-
=head1 ACKNOWLEDGEMENTS
There are a number of individuals that have really helped out with