【SQL腕試し問題】現在の部署に所属する社員の一覧を取得するSQLを書いて下さいの解答例

answer.sql

-- http://qiita.com/jnchito/items/29e22cc5a73da29f65a3
SELECT
  e.id
 ,e.name
 ,sh.section_name
 ,to_char(sh.start_date, 'yyyy/mm/dd') as start_date
FROM
  employees e
INNER JOIN
  section_histories sh
  ON sh.employee_id = e.id
WHERE
      sh.section_name = 'IT'
  AND sh.start_date =
        (SELECT MAX(sh2.start_date)
         FROM section_histories sh2
         WHERE sh.employee_id = sh2.employee_id)
ORDER BY
  e.id