Perl-DBIC/SELECT 基本のバックアップソース(No.14)

* SELECT [#g8767459]

http://search.cpan.org/perldoc?DBIx::Class::ResultSet#search

** FIND [#he6a13f8]
プライマリキーで検索する。見つからないときは、undefが返ってくる。
 my $cd = $schema->resultset('CD')->find(5);

** SEARCH [#u5289657]
 $rs->search({address => 'tokyo'},{order_by => ['name', 'id DESC']})
 $rs->search({age => {'>=' => 20}})
 $rs->search({hobby => undef}) # SQL:"hobby is null"

** LIKE / IN / OR [#xa2dd0d1]
 $rs->search_like({title => '%blue%'});                  # LIKE
 $rs->search({user_id => {-in => \@user_ids}})           # IN
 $rs->search([{address => '東京'},{address => '大阪'}]); # OR

** GROUP BY [#g35ffed7]
 $rs->search({},{
     select   => ['name',{sum=>'point'}],
     as       => ['name','point'],
     group_by => ['name'],
 });
 $point = $rs->next->get_column('point');

** COUNT() [#e0e28000]
 $rs = $rs->search();
 print $rs->count;
↓SELECT COUNT(DISTINCT name) FROM user
 $rs = $rs->seach({},{
   select => [ { count => { distinct => 'name' } } ],
    as    => ['count'],
 });
 print $rs->next->get_column('count');

** LIMIT / OFFSET [#y76174dc]
 $rs->search({},{ order_by => 'id' })->slice(0,20); # slice($offset,$limit)

** テーブル結合 [#w4bf664b]
*** JOIN （3つのテーブル） [#s1746a0e]
 SELECT order.* FROM order JOIN order_detail ON order.id = order_detail.order_id JOIN goods order_detail.goods_id = goods.id
 WHERE goods.name = 'book'

 $rs->search({
  "goods.name" => 'book',
 },{ 
   join => {order_detail => 'goods'}
 });

*** 自己結合 [#c1729252]
 SELECT XXX FROM category cate1 JOIN category cate2 ON cate1.parent_category_id = cate2.category_id

 $rs = $rs->search({},
     {
         from => [
             { cate1 => 'category' },
             [ { cate2 => 'category' }, { 'cate1.parent_category_id' => 'cate2.category_id' } ]
         ]
     }
 );

*** PREFETCH [#r9685ba3]
 $rs->search(undef,{prefetch => 'user', join => 'user'});
ジョインするテーブルをjoin=>'TABLE名'で明示する事。

** 特定のカラムのみSELECT（AS演算子）[#hf28370c]
 $rs->search({},{
    select => [ 'name', 'age' ],
    as     => [ 'name', '年齢'],
 });
 print $r->name, $r->get_column('年齢');

** DB関数 [#r24f677f]
*** DBの関数を比較の対象に使う [#zeced0ab]
 $rs->search({"date_part('year', age(now(), birth_date))" => { '<=' => 18 } }); # 年齢が18歳以下
                                                                                # date_part()とage()はPostgreSQLの関数
http://search.cpan.org/perldoc?DBIx::Class::Manual::Cookbook#Using_SQL_functions_on_the_left_hand_side_of_a_comparison
*** DBの関数を比較の値に使う [#z004db0c]
不等号「>」も含めて、スカラリファレンスにする。
 $rs->search( { start_day => \' > now()' } );