Learning mySQL but cant figure out this error

December 19, 2023

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
)

The sub-query is working fine, but it fails when I add the topmost query. Error is on DBFiddle

Query Error: Error: ER_PARSE_ERROR: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘as main )’ at line 26

I am trying to add top query because I have to perform more operations on it.

>Solution :

You must remove more than one bracket

Keeping all brackets on the same distance from he left is helpful to have clean code

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 drv