Perl-DBIC/SELECT 基本のバックアップ(No.26)

SELECT 基本

where句を設定する

 $rs->search({ age => 20 })                        # WHERE age = 20                   =
 $rs->search({ age => {'!=', 20} })                # WHERE age != 20                  !=
 $rs->search({ age => {'>' => 20} })               # WHERE age > 20                   >
 $rs->search({ age => undef })                     # WHERE age is NULL                NULL
 $rs->search([{ age => 20 },{ age => 30 }])        # WHERE age = 20 OR age = 30       OR
 $rs->search({ age => 20, name => 'taro })         # WHERE age = 20 AND name = 'taro' AND
 $rs->search({ age => { '>' => 10, '<' => 20 }})   # WHERE age > 10 AND age < 20      AND  同じカラムを使う場合
 $rs->search({ age => [10, 20] })                  # WHERE age BETWEEN 10 AND 20      BETWEEN
 $rs->search_like({ name => '%taro%' })            # WHERE name LIKE '%taro%'         LIKE
 $rs->search({ id => {-in => \@ids}})              # WHERE id in (1,2,3..)            IN

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

検索を実行する

 my $rs = $schema->resultset('User')->search({ age => 20});

プライマリキーで検索する

 my $user = $schema->resultset('User')->find(5);

見つからないときはundefが返ってくる。

検索結果を取り出す

順次取り出す

 while (my $user = $rs->next) { print $user->name; }

1行だけ取り出す

 my $user = $schema->resultset('User')->single({ age => 20});

最初の行を取り出す

 my $user = $schema->resultset('User')->search({ age => 20})->first;

全行取り出す

 my @users = $schema->resultset('User')->search({ age => 20})->all;

ORDER BY

 $rs->search({},{ 
  order_by => [ 'name', { -desc => 'id' } ] # ORDER BY name ASC, id DESC
  });                                       # 'name' は { -asc => 'name' } の省略形

http://search.cpan.org/perldoc?SQL::Abstract#ORDER_BY_CLAUSES

NULLを0と見なしてORDER BYする方法

（多分）DBICではCASE式が使えないので、COALESCE関数を使う。例えばpointカラムを降順でソートするには以下のようにする。

 $rs->search(undef, {
  order_by => [ { '-desc' => \'COALESCE(point, 0)' } ],
 });

GROUP BY

 $rs->search({},{
     select   => ['name', {SUM => 'point'}],
     as       => ['name', 'point'],
     group_by => ['name'],
 });
 $point = $rs->next->get_column('point');

LIMIT / OFFSET

 $rs->search({},{ order_by => 'id' })->slice(0,20); # slice($offset,$limit)

特定のカラムのみSELECT（AS演算子）

 $rs->search({},{
    select => [ 'name', 'age' ],
    as     => [ 'name', '年齢'],
 });
 print $r->name, $r->get_column('年齢');