正在学习mySQL,但无法解决此错误

select * from 
(
select year,
  subs,
  unsubs,
  LAG(subs,1) OVER(ORDER BY year) as sub_py,
  LAG(unsubs,1) OVER(ORDER BY year) as unsub_py
  FROM 
  (
    (
      SELECT
      DATE_FORMAT(subscription_started,"%Y") as year,
      SUM(Case WHEN subscription_started is not null then 1 else 0 end) as subs
      FROM user_churn
      group by year
    ) as s
    INNER JOIN
    (
      SELECT
      DATE_FORMAT(subscription_ended,"%Y") as year_unsub,
      SUM(Case WHEN subscription_ended is not null then 1 else 0 end) as unsubs
      FROM user_churn
      group by year_unsub
    ) as us
      on s.year=us.year_unsub
  ) as main
)

子查询工作正常,但添加最上面的查询时会失败。错误处于打开状态 DBFiddle

查询错误:错误:ER_PARSE_Error:您的SQL语法有错误;在第26行的“as main)”附近使用正确的语法,请查看与MySQL服务器版本对应的手册

我试图添加top查询,因为我必须对它执行更多操作。