SQL BigQuery - Error that variable is not grouped by even though it is

Question

SQL Code:

 SELECT community_table.community_name,
        community_table.id,
        DATE(timestamp) as date,
        ifnull(COUNT(distinct app_opened.user_id), 0) as num_opened_DAU,
        lag(COUNT(distinct app_opened.user_id)) OVER 
        (ORDER BY community_table.community_name, community_table.id, DATE(timestamp)) as pre_Value
        
        FROM *** app_opened

        LEFT JOIN (
          SELECT DISTINCT id, community_id_2, context_traits_first_name, context_traits_last_name
          FROM (
                SELECT *
                FROM ***,
                UNNEST (JSON_EXTRACT_ARRAY(context_traits_community_ids, "$")) as community_id_2
               ) 
          GROUP by community_id_2, id, context_traits_first_name, context_traits_last_name) as community_id_table
        ON community_id_table.id = app_opened.user_id

        LEFT JOIN (
          SELECT DISTINCT id, name as community_name
          FROM ***) as community_table
        ON TO_JSON_STRING(community_table.id) = community_id_table.community_id_2

        WHERE app_opened.user_id is not null AND 
              EXTRACT(DAYOFWEEK FROM DATE(timestamp)) = 2 AND
              community_table.community_name is not null
        GROUP BY community_table.community_name, community_table.id, DATE(timestamp)

Error Message:

I am quite confused on what could be going wrong here, as the error says that timestamp is not grouped, even though I have grouped it at the bottom. I tried including just timestamp rather than Date(timestamp), but that ruins the table data that I am trying to create, where I find the number of users on a single day. Does anyone have any other ideas? My goal is for a single row, get the previous row's data, but because I am grouping by specific metrics, I need to make sure they are ordered by them as well. Thank you so much!

Answer 1

I think you simply need to modify OVER part as:

OVER (PARTITION BY community_table.community_name, community_table.id, DATE(timestamp)) as pre_Value

UPDATE. Seems that the problem was caused by using DATE() function within OVER so it can be solved by using DATE(timestamp) inside of subquery and passing alias to OVER