postgresql "concatenate rows into string variable" code example

Example 1: postgresql combine values in one field

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