sql - 如何使用 COUNT、SUM、CASE 和 BETWEEN 将此 SQL 查询转换为 Perl DBIx::Class？

Question

如何将此 SQL 查询转换为 Perl DBIx::Class代码？

SELECT COUNT(*) AS num_grads,
       SUM(CASE WHEN employment_status = 1 THEN 1 ELSE 0 END) AS num_employed
  FROM students
 WHERE status = 6  -- 6 means they graduated
   AND grad_date BETWEEN Convert(datetime, ?) AND Convert(datetime, ?)

Answer 1

假设您的意思是 DBIx::Class，那么我可能会选择类似：

my $rs = My::Schema->resultset('Students') #
    ->search({
        status => 6,
        grad_date => { 'between' => [ $start_dt, $end_dt ] },
    });

my $num_grads    = $rs->count();
my $num_employed = $rs->search({ employment_status => 1 })->count();

当然，日期时间位将取决于您的日期时间格式，是否自动膨胀/放气日期时间等