Postgres 9.6

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CREATE TABLE "organisations"
AS
SELECT 1::integer "id",
       '[{"id":23,"role":"admin"},{"id":24,"role":"default"}]'::jsonb "members";

SELECT 1


CREATE TABLE "users"
AS
SELECT 23::integer "id",
       'Max'::text "name",
       'max@gmail.com'::text "email"
UNION ALL
SELECT 24::integer "id",
       'Joe'::text "name",
       'joe@gmail.com'::text "email";

SELECT 2


SELECT jsonb_agg(jsonb_build_object('id', "u"."id",
                                    'name', "u"."name",
                                    'email', "u"."email",
                                    'role', "m"."role"))
       FROM "organisations" "o"
            CROSS JOIN LATERAL jsonb_to_recordset(o."members") "m" ("id" integer,
                                                                    "role" text)
            INNER JOIN "users" "u"
                       ON "u"."id" = "m"."id";


jsonb_agg


[{"id": 24, "name": "Joe", "role": "default", "email": "joe@gmail.com"}, {"id": 23, "name": "Max", "role": "admin", "email": "max@gmail.com"}]



SELECT 1