package DBIx::Custom;

our $VERSION = '0.1619';

use 5.008001;

use strict;

use warnings;

use base 'Object::Simple';

use Carp 'croak';

use DBI;

use DBIx::Custom::Result;

use DBIx::Custom::Query;

use DBIx::Custom::QueryBuilder;

use Encode qw/encode_utf8 decode_utf8/;

__PACKAGE__->attr([qw/data_source dbh default_bind_filter

                      default_fetch_filter password user/]);

__PACKAGE__->attr(cache => 1);

__PACKAGE__->attr(cache_method => sub {

    sub {

        my $self = shift;

        $self->{_cached} ||= {};

        if (@_ > 1) {

            $self->{_cached}{$_[0]} = $_[1] 

        }

        else {

            return $self->{_cached}{$_[0]}

        }

    }

});

__PACKAGE__->dual_attr('filters', default => sub { {} },

                                  inherit => 'hash_copy');

__PACKAGE__->attr(filter_check => 1);

__PACKAGE__->attr(query_builder  => sub {DBIx::Custom::QueryBuilder->new});

__PACKAGE__->attr(result_class => 'DBIx::Custom::Result');

# DBI methods

foreach my $method (qw/begin_work commit rollback/) {

    my $code = sub {

        my $self = shift;

        my $ret = eval {$self->dbh->$method};

        croak $@ if $@;

        return $ret;

    };

    no strict 'refs';

    my $pkg = __PACKAGE__;

    *{"${pkg}::$method"} = $code;

};

# Regster filter

__PACKAGE__->register_filter(

    encode_utf8 => sub { encode_utf8($_[0]) },

    decode_utf8 => sub { decode_utf8($_[0]) }

);

our $AUTOLOAD;

sub AUTOLOAD {

    my $self = shift;

    # Method

    my ($package, $method) = $AUTOLOAD =~ /^([\w\:]+)\:\:(\w+)$/;

    # Helper

    $self->{_helpers} ||= {};

    croak qq/Can't locate object method "$method" via "$package"/

      unless my $helper = $self->{_helpers}->{$method};

    # Run

    return $self->$helper(@_);

}

sub helper {

    my $self = shift;

    # Merge

    my $helpers = ref $_[0] eq 'HASH' ? $_[0] : {@_};

    $self->{_helpers} = {%{$self->{_helpers} || {}}, %$helpers};

    return $self;

}

sub connect {

    my $proto = shift;

    # Create

    my $self = ref $proto ? $proto : $proto->new(@_);

    # Information

    my $data_source = $self->data_source;

    my $user        = $self->user;

    my $password    = $self->password;

    # Connect

    my $dbh = eval {DBI->connect(

        $data_source,

        $user,

        $password,

        {

            RaiseError => 1,

            PrintError => 0,

            AutoCommit => 1,

        }

    )};

    # Connect error

    croak $@ if $@;

    # Database handle

    $self->dbh($dbh);

    return $self;

}

sub create_query {

    my ($self, $source) = @_;

    # Cache

    my $cache = $self->cache;

    # Create query

    my $query;

    if ($cache) {

        # Get query

        my $q = $self->cache_method->($self, $source);

        # Create query

        $query = DBIx::Custom::Query->new($q) if $q;

    }

    unless ($query) {

        # Create SQL object

        my $builder = $self->query_builder;

        # Create query

        $query = $builder->build_query($source);

        # Cache query

        $self->cache_method->($self, $source,

                             {sql     => $query->sql, 

                              columns => $query->columns})

          if $cache;

    }

    # Prepare statement handle

    my $sth;

    eval { $sth = $self->dbh->prepare($query->{sql})};

    $self->_croak($@, qq{. SQL: "$query->{sql}"}) if $@;

    # Set statement handle

    $query->sth($sth);

    return $query;

}

our %VALID_DELETE_ARGS

  = map { $_ => 1 } qw/table where append filter allow_delete_all/;

sub delete {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_DELETE_ARGS{$name};

    }

    # Arguments

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

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

    my $append = $args{append};

    my $filter           = $args{filter};

    my $allow_delete_all = $args{allow_delete_all};

    # Where keys

    my @where_keys = keys %$where;

    # Not exists where keys

    croak qq{"where" argument must be specified and } .

          qq{contains the pairs of column name and value}

      if !@where_keys && !$allow_delete_all;

    # Where clause

    my $where_clause = '';

    if (@where_keys) {

        $where_clause = 'where ';

        $where_clause .= "{= $_} and " for @where_keys;

        $where_clause =~ s/ and $//;

    }

    # Source of SQL

    my $source = "delete from $table $where_clause";

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

    # Execute query

    my $ret_val = $self->execute($source, param  => $where, 

                                 filter => $filter);

    return $ret_val;

}

sub delete_all { shift->delete(allow_delete_all => 1, @_) }

sub DESTROY { }

our %VALID_EXECUTE_ARGS = map { $_ => 1 } qw/param filter/;

sub execute{

    my ($self, $query, %args)  = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_EXECUTE_ARGS{$name};

    }

    my $params = $args{param} || {};

    # First argument is the soruce of SQL

    $query = $self->create_query($query)

      unless ref $query;

    my $filter = $args{filter} || $query->filter || {};

    # Create bind value

    my $bind_values = $self->_build_bind_values($query, $params, $filter);

    # Execute

    my $sth      = $query->sth;

    my $affected;

    eval {$affected = $sth->execute(@$bind_values)};

    $self->_croak($@) if $@;

    # Return resultset if select statement is executed

    if ($sth->{NUM_OF_FIELDS}) {

        # Create result

        my $result = $self->result_class->new(

            sth            => $sth,

            default_filter => $self->default_fetch_filter,

            filters        => $self->filters,

            filter_check   => $self->filter_check

        );

        return $result;

    }

    return $affected;

}

sub expand {

    my $self = shift;

    my $source = ref $_[0] eq 'HASH' ? $_[0] : {@_};

    my $table = (keys %$source)[0];

    my $param = $source->{$table};

    # Expand table name

    my $expand = {};

    foreach my $column (keys %$param) {

        $expand->{"$table.$column"} = $param->{$column};

    }

    return %$expand;

}

our %VALID_INSERT_ARGS = map { $_ => 1 } qw/table param append filter/;

sub insert {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_INSERT_ARGS{$name};

    }

    # Arguments

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

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

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

    my $filter = $args{filter};

    # Insert keys

    my @insert_keys = keys %$param;

    # Templte for insert

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

               . join(' ', @insert_keys) . '}';

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

    # Execute query

    my $ret_val = $self->execute($source, param  => $param, 

                                          filter => $filter);

    return $ret_val;

}

sub register_filter {

    my $invocant = shift;

    # Register filter

    my $filters = ref $_[0] eq 'HASH' ? $_[0] : {@_};

    $invocant->filters({%{$invocant->filters}, %$filters});

    return $invocant;

}

our %VALID_SELECT_ARGS

  = map { $_ => 1 } qw/table column where append relation filter param/;

sub select {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_SELECT_ARGS{$name};

    }

    # Arguments

    my $tables = $args{table} || [];

    $tables = [$tables] unless ref $tables eq 'ARRAY';

    my $columns  = $args{column} || [];

    my $where    = $args{where};

    my $relation = $args{relation};

    my $append   = $args{append};

    my $filter   = $args{filter};

    # Source of SQL

    my $source = 'select ';

    # Column clause

    if (@$columns) {

        foreach my $column (@$columns) {

            $source .= "$column, ";

        }

        $source =~ s/, $/ /;

    }

    else {

        $source .= '* ';

    }

    # Table

    $source .= 'from ';

    foreach my $table (@$tables) {

        $source .= "$table, ";

    }

    $source =~ s/, $/ /;

    # Where clause

    my $param;

    if (ref $where eq 'HASH') {

        $param = $where;

        $source .= 'where (';

        foreach my $where_key (keys %$where) {

            $source .= "{= $where_key} and ";

        }

        $source =~ s/ and $//;

        $source .= ') ';

    }

    elsif (ref $where eq 'ARRAY') {

        my$where_str = $where->[0] || '';

        $param = $where->[1];

        $source .= "where ($where_str) ";

    }

    # Relation

    if ($relation) {

        $source .= $where ? "and " : "where ";

        foreach my $rkey (keys %$relation) {

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

        }

    }

    $source =~ s/ and $//;

    # Append some statement

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

    # Execute query

    my $result = $self->execute($source, param  => $param, 

                                         filter => $filter);

    return $result;

}

our %VALID_UPDATE_ARGS

  = map { $_ => 1 } qw/table param where append filter allow_update_all/;

sub update {

    my ($self, %args) = @_;

    # Check arguments

    foreach my $name (keys %args) {

        croak qq{"$name" is invalid argument}

          unless $VALID_UPDATE_ARGS{$name};

    }

    # Arguments

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

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

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

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

    my $filter           = $args{filter};

    my $allow_update_all = $args{allow_update_all};

    # Update keys

    my @update_keys = keys %$param;

    # Where keys

    my @where_keys = keys %$where;

    # Not exists where keys

    croak qq{"where" argument must be specified and } .

          qq{contains the pairs of column name and value}

      if !@where_keys && !$allow_update_all;

    # Update clause

    my $update_clause = '{update_param ' . join(' ', @update_keys) . '}';

    # Where clause

    my $where_clause = '';

    my $new_where = {};

    if (@where_keys) {

        $where_clause = 'where ';

        $where_clause .= "{= $_} and " for @where_keys;

        $where_clause =~ s/ and $//;

    }

    # Source of SQL

    my $source = "update $table $update_clause $where_clause";

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

    # Rearrange parameters

    foreach my $wkey (@where_keys) {

        if (exists $param->{$wkey}) {

            $param->{$wkey} = [$param->{$wkey}]

              unless ref $param->{$wkey} eq 'ARRAY';

            push @{$param->{$wkey}}, $where->{$wkey};

        }

        else {

            $param->{$wkey} = $where->{$wkey};

        }

    }

    # Execute query

    my $ret_val = $self->execute($source, param  => $param, 

                                 filter => $filter);

    return $ret_val;

}

sub update_all { shift->update(allow_update_all => 1, @_) };

sub _build_bind_values {

    my ($self, $query, $params, $filter) = @_;

    # binding values

    my @bind_values;

    # Filter

    $filter ||= {};

    # Parameter

    $params ||= {};

    # Check filter

    $self->_check_filter($self->filters, $filter,

                         $self->default_bind_filter, $params)

      if $self->filter_check;

    # Build bind values

    my $count = {};

    foreach my $column (@{$query->columns}) {

        # Value

        my $value = ref $params->{$column} eq 'ARRAY'

                  ? $params->{$column}->[$count->{$column} || 0]

                  : $params->{$column};

        # Filtering

        my $fname = $filter->{$column} || $self->default_bind_filter || '';

        my $filter_func = $fname ? $self->filters->{$fname} : undef;

        push @bind_values, $filter_func

                         ? $filter_func->($value)

                         : $value;

        # Count up 

        $count->{$column}++;

    }

    return \@bind_values;

}

sub _check_filter {

    my ($self, $filters, $filter, $default_filter, $params) = @_;

    # Filter name not exists

    foreach my $fname (values %$filter) {

        croak qq{Bind filter "$fname" is not registered}

          unless exists $filters->{$fname};

    }

    # Default filter name not exists

    croak qq{Default bind filter "$default_filter" is not registered}

      if $default_filter && ! exists $filters->{$default_filter};

    # Column name not exists

    foreach my $column (keys %$filter) {

        croak qq{Column name "$column" in bind filter is not found in paramters}

          unless exists $params->{$column};

    }

}

sub _croak {

    my ($self, $error, $append) = @_;

    $append ||= "";

    # Verbose

    if ($Carp::Verbose) { croak $error }

    # Not verbose

    else {

        # Remove line and module infromation

        my $at_pos = rindex($error, ' at ');

        $error = substr($error, 0, $at_pos);

        $error =~ s/\s+$//;

        croak "$error$append";

    }

}

1;

=head1 NAME

DBIx::Custom - DBI interface, having hash parameter binding and filtering system

=head1 SYNOPSYS

Connect to the database.

    use DBIx::Custom;

    my $dbi = DBIx::Custom->connect(data_source => "dbi:mysql:database=dbname",

                                    user => 'ken', password => '!LFKD%$&');

Insert, update, and delete

    # Insert 

    $dbi->insert(table  => 'books',

                 param  => {title => 'Perl', author => 'Ken'},

                 filter => {title => 'encode_utf8'});

    # Update 

    $dbi->update(table  => 'books', 

                 param  => {title => 'Perl', author => 'Ken'}, 

                 where  => {id => 5},

                 filter => {title => 'encode_utf8'});

    # Update all

    $dbi->update_all(table  => 'books',

                     param  => {title => 'Perl'},

                     filter => {title => 'encode_utf8'});

    # Delete

    $dbi->delete(table  => 'books',

                 where  => {author => 'Ken'},

                 filter => {title => 'encode_utf8'});

    # Delete all

    $dbi->delete_all(table => 'books');

Select

    # Select

    my $result = $dbi->select(table => 'books');

    # Select, more complex

    my $result = $dbi->select(

        table  => 'books',

        column => [qw/author title/],

        where  => {author => 'Ken'},

        append => 'order by id limit 5',

        filter => {title => 'encode_utf8'}

    );

    # Select, join table

    my $result = $dbi->select(

        table    => ['books', 'rental'],

        column   => ['books.name as book_name']

        relation => {'books.id' => 'rental.book_id'}

    );

    # Select, more flexible where

    my $result = $dbi->select(

        table  => 'books',

        where  => ['{= author} and {like title}', 

                   {author => 'Ken', title => '%Perl%'}]

    );

Execute SQL

    # Execute SQL

    $dbi->execute("select title from books");

    # Execute SQL with hash binding and filtering

    $dbi->execute("select id from books where {= author} and {like title}",

                  param  => {author => 'ken', title => '%Perl%'},

                  filter => {title => 'encode_utf8'});

    # Create query and execute it

    my $query = $dbi->create_query(

        "select id from books where {= author} and {like title}"

    );

    $dbi->execute($query, param => {author => 'Ken', title => '%Perl%'})

Other features.

    # Default filter

    $dbi->default_bind_filter('encode_utf8');

    $dbi->default_fetch_filter('decode_utf8');

    # Get DBI object

    my $dbh = $dbi->dbh;

Fetch row.

    # Fetch

    while (my $row = $result->fetch) {

        # ...

    }

    # Fetch hash

    while (my $row = $result->fetch_hash) {

    }

=head1 DESCRIPTIONS

L<DBIx::Custom> is one of L<DBI> interface modules,

such as L<DBIx::Class>, L<DBIx::Simple>.

This module is not O/R mapper. O/R mapper is useful,

but you must learn many syntax of the O/R mapper,

which is almost another language.

Created SQL statement is offten not effcient and damage SQL performance.

so you have to execute raw SQL in the end.

L<DBIx::Custom> is middle area between L<DBI> and O/R mapper.

L<DBIx::Custom> provide flexible hash parameter binding and filtering system,

and suger methods, such as C<insert()>, C<update()>, C<delete()>, C<select()>

to execute SQL easily.

L<DBIx::Custom> respects SQL. SQL is very complex and not beautiful,

but de-facto standard,

so all people learing database know it.

If you already know SQL,

you learn a little thing to use L<DBIx::Custom>.

See L<DBIx::Custom::Guides> for more details.

=head1 ATTRIBUTES

=head2 C<cache>

    my $cache = $dbi->cache;

    $dbi      = $dbi->cache(1);

Enable parsed L<DBIx::Custom::Query> object caching.

Default to 1.

=head2 C<cache_method>

    $dbi          = $dbi->cache_method(\&cache_method);

    $cache_method = $dbi->cache_method

Method to set and get caches.

B<Example:>

    $dbi->cache_method(

        sub {

            my $self = shift;

            $self->{_cached} ||= {};

            if (@_ > 1) {

                $self->{_cached}{$_[0]} = $_[1] 

            }

            else {

                return $self->{_cached}{$_[0]}

            }

        }

    );

=head2 C<data_source>

    my $data_source = $dbi->data_source;

    $dbi            = $dbi->data_source("DBI:mysql:database=dbname");

Data source.

C<connect()> method use this value to connect the database.

=head2 C<dbh>

    my $dbh = $dbi->dbh;

    $dbi    = $dbi->dbh($dbh);

L<DBI> object. You can call all methods of L<DBI>.

=head2 C<default_bind_filter>

    my $default_bind_filter = $dbi->default_bind_filter

    $dbi                    = $dbi->default_bind_filter('encode_utf8');

Default filter when parameter binding is executed.

=head2 C<default_fetch_filter>

    my $default_fetch_filter = $dbi->default_fetch_filter;

    $dbi                     = $dbi->default_fetch_filter('decode_utf8');

Default filter when row is fetched.

=head2 C<filters>

    my $filters = $dbi->filters;

    $dbi        = $dbi->filters(\%filters);

Filter functions.

"encode_utf8" and "decode_utf8" is registered by default.

=head2 C<filter_check>

    my $filter_check = $dbi->filter_check;

    $dbi             = $dbi->filter_check(0);

Enable filter check. 

Default to 1.

This check maybe damege performance.

If you require performance, set C<filter_check> attribute to 0.

=head2 C<password>

    my $password = $dbi->password;

    $dbi         = $dbi->password('lkj&le`@s');

Password.

C<connect()> method use this value to connect the database.

=head2 C<query_builder>

    my $sql_class = $dbi->query_builder;

    $dbi          = $dbi->query_builder(DBIx::Custom::QueryBuilder->new);

SQL builder. C<query_builder()> must be 

the instance of L<DBIx::Custom::QueryBuilder> subclass.

Default to L<DBIx::Custom::QueryBuilder> object.

=head2 C<result_class>

    my $result_class = $dbi->result_class;

    $dbi             = $dbi->result_class('DBIx::Custom::Result');

Result class for select statement.

Default to L<DBIx::Custom::Result>.

=head2 C<user>

    my $user = $dbi->user;

    $dbi     = $dbi->user('Ken');

User name.

C<connect()> method use this value to connect the database.

=head1 METHODS

L<DBIx::Custom> inherits all methods from L<Object::Simple>

and implements the following new ones.

=head2 begin_work

    $dbi->begin_work;

Start transaction.

This is same as L<DBI>'s C<begin_work>.

L<DBIx::Custom> inherits all methods from L<Object::Simple>

and implements the following new ones.

=head2 commit

    $dbi->commit;

Commit transaction.

This is same as L<DBI>'s C<commit>.

=head2 C<connect>

    my $dbi = DBIx::Custom->connect(data_source => "dbi:mysql:database=dbname",

                                    user => 'ken', password => '!LFKD%$&');

Create a new L<DBIx::Custom> object and connect to the database.

L<DBIx::Custom> is a wrapper of L<DBI>.

C<AutoCommit> and C<RaiseError> options are true, 

and C<PrintError> option is false by default. 

=head2 C<create_query>

    my $query = $dbi->create_query(

        "select * from books where {= author} and {like title};"

    );

Create the instance of L<DBIx::Custom::Query> from the source of SQL.

If you want to get high performance,

use C<create_query()> method and execute it by C<execute()> method

instead of suger methods.

    $dbi->execute($query, {author => 'Ken', title => '%Perl%'});

=head2 C<execute>

    my $result = $dbi->execute($query,  param => $params, filter => \%filter);

    my $result = $dbi->execute($source, param => $params, filter => \%filter);

Execute query or the source of SQL.

Query is L<DBIx::Custom::Query> object.

Return value is L<DBIx::Custom::Result> if select statement is executed,

or the count of affected rows if insert, update, delete statement is executed.

B<Example:>

    my $result = $dbi->execute(

        "select * from books where {= author} and {like title}", 

        param => {author => 'Ken', title => '%Perl%'}

    );

    while (my $row = $result->fetch) {

        my $author = $row->[0];

        my $title  = $row->[1];

    }

=head2 C<(experimental) expand>

    my %expand = $dbi->expand($source);

The following hash

    {books => {title => 'Perl', author => 'Ken'}}

is expanded to

    ('books.title' => 'Perl', 'books.author' => 'Ken')

This is used in C<select()>

=head2 C<delete>

    $dbi->delete(table  => $table,

                 where  => \%where,

                 append => $append,

                 filter => \%filter);

Execute delete statement.

C<delete> method have C<table>, C<where>, C<append>, and C<filter> arguments.

C<table> is a table name.

C<where> is where clause. this must be hash reference.

C<append> is a string added at the end of the SQL statement.

C<filter> is filters when parameter binding is executed.

Return value of C<delete()> is the count of affected rows.

B<Example:>

    $dbi->delete(table  => 'books',

                 where  => {id => 5},

                 append => 'some statement',

                 filter => {id => 'encode_utf8'});

=head2 C<delete_all>

    $dbi->delete_all(table => $table);

Execute delete statement to delete all rows.

Arguments is same as C<delete> method,

except that C<delete_all> don't have C<where> argument.

Return value of C<delete_all()> is the count of affected rows.

B<Example:>

    $dbi->delete_all(table => 'books');

=head2 C<(experimental) helper>

    $dbi->helper(

        update_or_insert => sub {

            my $self = shift;

            # do something

        },

        find_or_create   => sub {

            my $self = shift;

            # do something

        }

    );

Register helper methods. These method is called from L<DBIx::Custom> object directory.

    $dbi->update_or_insert;

    $dbi->find_or_create;

=head2 C<insert>

    $dbi->insert(table  => $table, 

                 param  => \%param,

                 append => $append,

                 filter => \%filter);

Execute insert statement.

C<insert> method have C<table>, C<param>, C<append>

and C<filter> arguments.

C<table> is a table name.

C<param> is the pairs of column name value. this must be hash reference.

C<append> is a string added at the end of the SQL statement.

C<filter> is filters when parameter binding is executed.

This is overwrites C<default_bind_filter>.

Return value of C<insert()> is the count of affected rows.

B<Example:>

    $dbi->insert(table  => 'books', 

                 param  => {title => 'Perl', author => 'Taro'},

                 append => "some statement",

                 filter => {title => 'encode_utf8'})

=head2 C<register_filter>

    $dbi->register_filter(%filters);

    $dbi->register_filter(\%filters);

Register filter. Registered filters is available in the following attributes

or arguments.

=over 4

=item *

C<default_bind_filter>, C<default_fetch_filter>

=item *

C<filter> argument of C<insert()>, C<update()>,

C<update_all()>, C<delete()>, C<delete_all()>, C<select()>

methods

=item *

C<execute()> method

=item *

C<default_filter> and C<filter> of C<DBIx::Custom::Query>

=item *

C<default_filter> and C<filter> of C<DBIx::Custom::Result>

=back

B<Example:>

    $dbi->register_filter(

        encode_utf8 => sub {

            my $value = shift;

            require Encode;

            return Encode::encode('UTF-8', $value);

        },

        decode_utf8 => sub {

            my $value = shift;

            require Encode;

            return Encode::decode('UTF-8', $value)

        }

    );

=head2 rollback

    $dbi->rollback;

Rollback transaction.

This is same as L<DBI>'s C<rollback>.

=head2 C<select>

    my $result = $dbi->select(table    => $table,

                              column   => [@column],

                              where    => \%where,

                              append   => $append,

                              relation => \%relation,

                              filter   => \%filter);

Execute select statement.

C<select> method have C<table>, C<column>, C<where>, C<append>,

C<relation> and C<filter> arguments.

C<table> is a table name.

C<where> is where clause. this is normally hash reference.

C<append> is a string added at the end of the SQL statement.

C<filter> is filters when parameter binding is executed.

B<Example:>

    # select * from books;

    my $result = $dbi->select(table => 'books');

    # select * from books where title = ?;

    my $result = $dbi->select(table => 'books', where => {title => 'Perl'});

    # select title, author from books where id = ? for update;

    my $result = $dbi->select(

        table  => 'books',

        column => ['title', 'author'],

        where  => {id => 1},

        appned => 'for update'

    );

    # select books.name as book_name from books, rental

    # where books.id = rental.book_id;

    my $result = $dbi->select(

        table    => ['books', 'rental'],

        column   => ['books.name as book_name']

        relation => {'books.id' => 'rental.book_id'}

    );

If you use more complex condition,

you can specify a array reference to C<where> argument.

    my $result = $dbi->select(

        table  => 'books',

        column => ['title', 'author'],

        where  => ['{= title} or {like author}',

                   {title => '%Perl%', author => 'Ken'}]

    );

First element is a string. it contains tags,

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

Second element is paramters.

=head2 C<update>

    $dbi->update(table  => $table, 

                 param  => \%params,

                 where  => \%where,