ARRAY_AGG

MySQL equivalent:

Collects the values of a group of rows into an array.

PostgreSQL 17.5

ARRAY_AGG([DISTINCT] expression [ORDER BY ...])

Parameters

An array of values of the same type, NULLs included; NULL for an empty set

PostgreSQL 17.5

SELECT ARRAY_AGG(
		n
		ORDER BY n DESC
	)
FROM GENERATE_SERIES(1, 5) AS n;

array_agg
54321

PostgreSQL 17.5

SELECT status,
	ARRAY_AGG(member_name) AS members
FROM FamilyMembers
GROUP BY status
ORDER BY status;

status	members
daughter	Lela QuinceyAnnie QuinceyWednesday Addams
father	Headley QuinceyErnest Forrest
mother	Flavia QuinceyConstance Forrest
son	Andie Quincey

Unlike STRING_AGG, ARRAY_AGG does not skip NULL values. Without ORDER BY the order of the elements is not guaranteed.

Array elements are numbered from 1: the expression (ARRAY_AGG(member_name ORDER BY birthday))[1] returns the name of the oldest family member.