Select records and related entity count

Given the following select that will count related entities for every record SELECT MAIN.*, SUB.app_count FROM my_table_view MAIN LEFT JOIN (SELECT MAIN2.p_key, count(DISTINCT T3.app_id) AS app_count FROM my_table MAIN2 JOIN T1 ... LEFT JOIN T2 ... LEFT JOIN T3 ... GROUP BY MAIN2.p_key) SUB ON MAIN.p_key = SUB.p_key WHERE ... Trying to simplify it, came up with the following : SELECT MAIN.p_key, count(DISTINCT T3.app_id) AS app_count -- select MAIN.* errors out - missing GROUP BY FROM my_table_view MAIN LEFT JOIN T1 ON ... LEFT JOIN T2 ON ... LEFT JOIN T3 ON ... WHERE ... GROUP BY MAIN.p_key How to select all data from the MAIN table without adding a bunch of GROUP BYs ? Would also appreciate performance hints. ### Edit I think this is related https://dba.stackexchange.com/questions/195104/postgres-group-by-id-works-on-table-directly-but-not-on-identical-view