NAME

DBIx::Interp - Interpolate Perl variables into SQL with DBI

SYNOPSIS

  use DBI;
  use DBIx::Interp ':all';

  my $dbx = DBIx::Interp->new($dbh);

  my $rv = $dbx->do_i('INSERT INTO table', \%item);
  my $rv = $dbx->do_i('UPDATE table SET',  \%item, 'WHERE item_id <> ', \2);
  my $rv = $dbx->do_i('DELETE FROM table WHERE item_id = ', \2);

  my $LoH = $dbx->selectall_arrayref_i('
        SELECT * FROM table WHERE x = ', \$s, 'AND y IN', \@v
        ,attr(Slice=>{}));

DESCRIPTION

DBIx::Interp brings SQL::Interp and DBI together in a natural way. Please read the documentation of those two modules if you are unfamiliar with them. The DBIx::Interp interface adds methods to the DBI interface with an "_i" suffix, indicating that SQL::Interp interpolatation is performed in these cases.

Note that this module is no longer used by the maintainer. DBIx::Simple now features SQL::Interp integration and is the recommended alternative.

Helper Functions you may need

"attr"

  dbi_interp("SELECT * from my_table", attr( Slice => {} ) );

Creates and returns an DBIx::Interp::Attr object. When processed by dbi_interp(), it will add the provided key/value pairs to the "%attrs" hash that is accepted by many DBI methods.

"key_field"

  $keyobj = key_field($key_field);

Creates and returns an DBIx::Interp::Key object. When processed by dbi_interp(), an extra $key_field value will be returned in the result so that the result is suitable for passing into $dbh->fetchrow_hashref and related methods.

  my ($sql, $key, $attr, @bind) =
  my @params = dbi_interp "SELECT * FROM mytable", key_field('itemid');
  $dbh->selectall_hashref(@params);

Database object (DBX) methods

An object of type DBIx::Interp represents (and wraps) a database handle. Most of its methods are wrappers around corresponding DBI methods.

"new" (static method)

 my $dbx = DBIx::Interp->new($db, %params);

Creates a new object, creating or attaching a DBI handle.

$db is either a DBI database handle or an ARRAYREF containing parameters that will be passed to DBI::connect, e.g. [$data_source, $username, $auth, \%attr]. This parameter may be omitted.

Any additional %params are passed onto SQL::Interp::new.

"connect" (static method)

 $dbx = DBIx::Interp->connect($data_source, $username, $auth, \%attr);

Connects to a database.

This is identical to DBI::connect except that it returns at DBIx::Interp object. An alternate way to connect or attach an existing DBI handle is via the "new" method.

"dbh"

 $dbh = $dbx->dbh();

Returns the underlying DBI handle $dbh. The is useful if you need to pass the DBI handle to code that does not use SQL::Interp.

 $dbx->dbh()->selectall_arrayref(
     "SELECT * FROM mytable WHERE x = ?", undef, $x);

"stx"

 $stx = $dbx->stx();

Returns the underlying statement handle set $stx. (These are discussed later.) Each DBIx::Interp object contains one statement handle set for use on non-prepared database calls (e.g. selectall_.*() methods).

 $dbx->stx()->max_sths(10);

do_i

selectall_arrayref_i

selectall_hashref_i

selectcol_arrayref_i

selectrow_array_i

selectrow_arrayref_i

selectrow_hashref_i

These methods are identical to those in DBI except interpolation is performed via SQL::Interp.

prepare

 $stx = $dbx->prepare();

Creates a new statement handle set ($stx of type SQL::Interp::STX) associated with $dbx. There are no parameters.

A statement handle set (stx) is an abstraction of a statement handle and represents an entire set of statement handles for a given class of SQL queries. This abstraction is used because a single interpolation list may interpolate into any number of SQL queries (depending on variable input), so multiple statement handles may need to be managed and cached. Typically, you do not need to call "prepare" directly because DBIx::Interp can transparently mangage a statement handle set (see $dbx->stx()->max_sths(10)).

Up to one statement handle in a set is considered active. Other operations performed on the statement handle set are passed to the active statement handle so that the statement handle set often looks and feels like a regular statement handle.

Statement handle set (STX) methods

These methods are for statement handle set objects.

"new"

  $stx = SQL::Interp::STX->new($dbx);

Creates a new statement handle set. Typically this is not called directly but rather is invoked through "prepare()".

"max_sths"

  $max_sths = $stx->max_sths(); # get
  $stx->max_sths($max_sths);    # set

Gets or sets the maximum number of statement handles to cache in the statement handle set. The default and minimum value is 1.

"sth"

  $sth = $stx->sth();

Gets the current active statement handle (e.g. the only that was just executed). Returns undef on none.

"sths"

  $sths = $stx->sths();

Return a hashref of contained statement handles (map: $sql -> $sth).

"execute"

  $rv = $stx->execute(@list);

Executes the query in the given interpolation list against a statement handle. If no statement matching statement handle exists, a new one is prepared. The used statement handle is made the active statement handle. Return on error behavior is similar to DBI's execute.

@list is an interpolation list (suitable for passing to "dbi_interp()").

"fetch..."

  $ary_ref = $stx->fetchrow_arrayref();

Various fetch.* methods analogous to those in DBIx::Interp are available. The fetch will be performed against the active statement handle in the set.

These are more advanced examples.

Binding variable types (DBI bind_param)

Compare this much simpler code to the example in SQL::Interp.

  $dbx->selectall_arrayref(
      "SELECT * FROM mytable WHERE",
      "x=", \$x, "AND y=", sql_type(\$y, SQL_VARCHAR), "AND z IN",
      sql_type([1, 2], SQL_INTEGER)
  );

DESIGN NOTES

Philosophy and requirements

DBIx::Interp is designed to look an feel like DBI even when the DBI interface is not entirely user friendly (e.g. the (fetch|select)(all|row)?_(array|hash)(ref)? and do methods). Still, the approach lowers the learning code and could simplify the process of converting existing DBI code over to SQL::Interp.

The use of statement handle sets (STX) is not strictly necessary but is rather designed to mimic DBI's statement handles more than anything else. The DBX object itself contains a statement handle set, which can be used for non-prepared calls such as to selectall_.*() methods (i.e. cache statement handles like in DBIx::Simple's keep_statements).

  $dbx->stx()->max_sths(2);
  $dbx->do(...) for 1..5;
  $dbx->do(...) for 1..5;

An ideal solution would probably be to integrate SQL::Interp into DBIx::Simple rather than directly into DBI.

Proposed enhancements

The following enhancements to SQL::Interp have been proposed. The most important suggestions are listed at top, and some suggestions could be rejected.

DBI database handle and statement handle attributes are not currently exposed from the wrapper except via $dbx->dbh()->{...}. Maybe a Tie can be used. e.g. $dbx->{mysql_insert_id}

Support might be added for something analogous to DBI's bind_param_inout.

DBI's bind_param_array is not currently supported. A syntax as follows might be used:

  "INSERT INTO mytable", [[...], [...], ...]

Passing identified variables:

  my $x = {one => 'two'};
  my $stx = $dbx->prepare("SELECT * FROM mytable WHERE", sql_type(\$x);
  $stx->execute_vars();
  ...
  $x->{two} = 'three';
  $stx->execute_vars();
  ...

  my $x = {one => 'two'};
  my $y = {one => 'three', two => 'four'};
  my $stx = $dbx->prepare("SELECT * FROM mytable WHERE", sql_type($x, 'x'));
  $stx->execute_vars();
  ...
  $stx->execute_vars(sql_type($x, 'x'); # or?
  $stx->execute_vars(x => $x); # or?
  ...

CONTRIBUTORS

David Manura (<http://math2.org/david>) (author). The existence and original design of this module as a wrapper around DBI was suggested by Jim Cromie.

FEEDBACK

Bug reports and comments on the design are most welcome. See the main SQL::Interp module for details.

LEGAL

Copyright (c) 2004-2005, David Manura. This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself. See <http://www.perl.com/perl/misc/Artistic.html>.