@@ -633,30 +633,17 @@ sub select {

     $columns = [$columns] unless ref $columns;

     my $selection = $args{selection} || '';

     my $where     = $args{where} || {};

-    my $relation  = $args{relation} || {};

     my $append    = $args{append};

     my $filter    = $args{filter};

     my $left_join = $args{left_join} || [];

+    croak qq{"left_join" must be array reference}

+      unless ref $left_join eq 'ARRAY';

-    my @left_join_tables;

-    unshift @left_join_tables, $tables->[-1];

+    my @join_tables;

+    unshift @join_tables, $tables->[-1];

-    # Relation

-    if (!$selection && keys %$relation) {

-        foreach my $rcolumn (keys %$relation) {

-            my $table1 = (split (/\./, $rcolumn))[0];

-            my $table2 = (split (/\./, $relation->{$rcolumn}))[0];

-            

-            my $table1_exists;

-            my $table2_exists;

-            foreach my $table (@$tables) {

-                $table1_exists = 1 if $table eq $table1;

-                $table2_exists = 1 if $table eq $table2;

-            }

-            unshift @$tables, $table1 unless $table1_exists;

-            unshift @$tables, $table2 unless $table2_exists;

-        }

-    }

+    # Relation table(DEPRECATED!);

+    $self->_add_relation_table($args{relation}, $tables);

     # SQL stack

     my @sql;

@@ -665,13 +652,13 @@ sub select {

     if ($selection) {

         push @sql, $selection;

-        push @left_join_tables, @{$self->_tables($selection)};

+        push @join_tables, @{$self->_tables($selection)};

     }

     else {

         # Column clause

         if (@$columns) {

             foreach my $column (@$columns) {

-                push @left_join_tables, @{$self->_tables($column)};

+                push @join_tables, @{$self->_tables($column)};

                 push @sql, ($column, ',');

             }

             pop @sql if $sql[-1] eq ',';

@@ -708,7 +695,7 @@ sub select {

     my $swhere = "$w";

     # Table name in Where

-    unshift @left_join_tables, @{$self->_tables($swhere)};

+    unshift @join_tables, @{$self->_tables($swhere)};

     # Left join

     if (@$left_join) {

@@ -722,7 +709,7 @@ sub select {

             my $table1_exists;

             my $table2_exists;

-            foreach my $table (@left_join_tables) {

+            foreach my $table (@join_tables) {

                 $table1_exists = 1 if $table eq $table1;

                 $table2_exists = 1 if $table eq $table2;

             }

@@ -736,19 +723,9 @@ sub select {

     # Add where

     push @sql, $swhere;

-    # Relation

-    if (!$selection && keys %$relation) {

-        push @sql, $swhere eq '' ? 'where' : 'and';

-        foreach my $rcolumn (keys %$relation) {

-            my $table1 = (split (/\./, $rcolumn))[0];

-            my $table2 = (split (/\./, $relation->{$rcolumn}))[0];

-            push @$tables, ($table1, $table2);

-            

-            push @sql, ("$rcolumn = " . $relation->{$rcolumn},  'and');

-        }

-    }

-    pop @sql if $sql[-1] eq 'and';

-        

+    # Relation(DEPRECATED!);

+    $self->_push_relation(\@sql, $tables, $args{relation}, $swhere eq '' ? 1 : 0);

+    

     # Append statement

     push @sql, $append if $append;

@@ -759,7 +736,7 @@ sub select {

     my $query = $self->create_query($sql);

     return $query if $args{query};

-    unshift @$tables, @left_join_tables;

+    unshift @$tables, @join_tables;

     # Execute query

     my $result = $self->execute(

@@ -1157,6 +1134,8 @@ sub _tables {

     return $tables;

 }

+

+

 # DEPRECATED!

 __PACKAGE__->attr(

     dbi_options => sub { {} },

@@ -1213,6 +1192,42 @@ sub register_tag_processor {

     return shift->query_builder->register_tag_processor(@_);

 }

+# DEPRECATED!

+sub _push_relation {

+    my ($self, $sql, $tables, $relation, $need_where) = @_;

+    

+    if (keys %{$relation || {}}) {

+        push @$sql, $need_where ? 'where' : 'and';

+        foreach my $rcolumn (keys %$relation) {

+            my $table1 = (split (/\./, $rcolumn))[0];

+            my $table2 = (split (/\./, $relation->{$rcolumn}))[0];

+            push @$tables, ($table1, $table2);

+            push @$sql, ("$rcolumn = " . $relation->{$rcolumn},  'and');

+        }

+    }

+    pop @$sql if $sql->[-1] eq 'and';    

+}

+

+# DEPRECATED!

+sub _add_relation_table {

+    my ($self, $relation, $tables) = @_;

+    

+    if (keys %{$relation || {}}) {

+        foreach my $rcolumn (keys %$relation) {

+            my $table1 = (split (/\./, $rcolumn))[0];

+            my $table2 = (split (/\./, $relation->{$rcolumn}))[0];

+            my $table1_exists;

+            my $table2_exists;

+            foreach my $table (@$tables) {

+                $table1_exists = 1 if $table eq $table1;

+                $table2_exists = 1 if $table eq $table2;

+            }

+            unshift @$tables, $table1 unless $table1_exists;

+            unshift @$tables, $table2 unless $table2_exists;

+        }

+    }

+}

+

 1;

 =head1 NAME

@@ -1733,6 +1748,7 @@ This is same as L<DBI>'s C<rollback>.

         where     => \%where,

         append    => $append,

         relation  => \%relation,

+        left_join => ['book.company_id' => 'company.id']

         filter    => \%filter,

         query     => 1,

         selection => $selection

@@ -1757,6 +1773,9 @@ First element is a string. it contains tags,

 such as "{= title} or {like author}".

 Second element is paramters.

+C<left_join> is add left outer join clause after from clause.

+This is experimental.

+

 =head3 C<(experimental) select_at()>

 To select row by using primary key, use C<select_at()>.

@@ -1722,3 +1722,29 @@ is($dbi->select(table => 'table1')->fetch_hash_first->{key1}, 1);

 eval { $dbi->insert_param({";" => 1}) };

 like($@, qr/not safety/);

+

+

+test 'left_join';

+$dbi = DBIx::Custom->connect($NEW_ARGS->{0});

+$dbi->execute($CREATE_TABLE->{0});

+$dbi->insert(table => 'table1', param => {key1 => 1, key2 => 2});

+$dbi->insert(table => 'table1', param => {key1 => 3, key2 => 4});

+$dbi->execute($CREATE_TABLE->{2});

+$dbi->insert(table => 'table2', param => {key1 => 1, key3 => 5});

+$rows = $dbi->select(

+    table => 'table1',

+    column => 'table1.key1 as table1_key1, table2.key1 as table2_key1, key2, key3',

+    where   => {'table1.key2' => 2},

+    left_join  => ['table1.key1' => 'table2.key1']

+)->fetch_hash_all;

+is_deeply($rows, [{table1_key1 => 1, table2_key1 => 1, key2 => 2, key3 => 5}]);

+

+eval {

+    $rows = $dbi->select(

+        table => 'table1',

+        column => 'table1.key1 as table1_key1, table2.key1 as table2_key1, key2, key3',

+        where   => {'table1.key2' => 2},

+        left_join  => {'table1.key1' => 'table2.key1'}

+    );

+};

+like ($@, qr/array/);