create another category as sum of value of two categories psql code example

Example 1: how to combine diff colmun value using group by postgres

SELECT movie, string_agg(actor, ', ' ORDER BY actor) AS actor_list
FROM   tbl
GROUP  BY 1;

Example 2: how to combine diff colmun value using group by postgres

SELECT movie, string_agg(actor, ', ') AS actor_list
FROM   tbl
GROUP  BY 1;