@@ -262,12 +262,17 @@ sub delete {

     croak qq{"where" must be specified}

       if $swhere eq '' && !$allow_delete_all;

-    # Source of SQL

-    my $source = "delete from $table $swhere";

-    $source .= " $append" if $append;

+    # SQL stack

+    my @sql;

+

+    # Delete

+    push @sql, "delete from $table $swhere";

+    push @sql, $append if $append;

+    

+    my $sql = join(' ', @sql);

     # Create query

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

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

     return $query if $args{query};

     # Execute query

@@ -389,13 +394,18 @@ sub insert {

         push @columns, $column;

     }

+    # SQL stack

+    my @sql;

+    

+    # Insert

+    push @sql, "insert into $table {insert_param ". join(' ', @columns) . '}';

+    push @sql, $append if $append;

+    

     # SQL

-    my $source = "insert into $table {insert_param "

-               . join(' ', @columns) . '}';

-    $source .= " $append" if $append;

+    my $sql = join (' ', @sql);

     # Create query

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

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

     return $query if $args{query};

     # Execute query

@@ -493,26 +503,26 @@ sub select {

     my $append   = $args{append};

     my $filter   = $args{filter};

-    # Source of SQL

-    my $source = 'select ';

+    # SQL stack

+    my @sql;

+    

+    push @sql, 'select';

     # Column clause

     if (@$columns) {

         foreach my $column (@$columns) {

-            $source .= "$column, ";

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

         }

-        $source =~ s/, $/ /;

-    }

-    else {

-        $source .= '* ';

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

     }

+    else { push @sql, '*' }

     # Table

-    $source .= 'from ';

+    push @sql, 'from';

     foreach my $table (@$tables) {

-        $source .= "$table, ";

+        push @sql, ($table, ',');

     }

-    $source =~ s/, $/ /;

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

     # Where

     my $w;

@@ -533,22 +543,25 @@ sub select {

     # String where

     my $swhere = "$w";

-    $source .= "$swhere ";

+    push @sql, $swhere;

     # Relation

     if ($relation) {

-        $source .= $swhere eq '' ? "where " : "and ";

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

-            $source .= "$rkey = " . $relation->{$rkey} . " and ";

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

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

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

         }

     }

-    $source =~ s/ and $//;

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

+    

+    # Append statement

+    push @sql, $append if $append;

-    # Append some statement

-    $source .= " $append" if $append;

+    # SQL

+    my $sql = join (' ', @sql);

     # Create query

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

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

     return $query if $args{query};

     # Execute query

@@ -651,9 +664,12 @@ sub update {

     croak qq{"where" must be specified}

       if "$swhere" eq '' && !$allow_update_all;

-    # Source of SQL

-    my $source = "update $table $update_clause $swhere";

-    $source .= " $append" if $append;

+    # SQL stack

+    my @sql;

+    

+    # Update

+    push @sql, "update $table $update_clause $swhere";

+    push @sql, $append if $append;

     # Rearrange parameters

     foreach my $wkey (keys %$where) {

@@ -669,8 +685,11 @@ sub update {

         }

     }

+    # SQL

+    my $sql = join(' ', @sql);

+    

     # Create query

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

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

     return $query if $args{query};

     # Execute query