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
)

字符串
子查询工作正常，但当我添加最顶层的查询时，它失败了。
查询错误：错误：ER_PARSE_ERROR：您的SQL语法中有一个错误;请检查与您的MySQL服务器版本对应的手册，以获得在第26行'as main）'附近使用的正确语法
我试图添加顶级查询，因为我必须对它执行更多操作。