Postgres 15

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE user_tasks (
    id                      bigserial            PRIMARY KEY,
    type                    varchar(255)         NOT NULL
);

INSERT INTO user_tasks (type) VALUES ('type1'), ('type1'), ('type1'), ('type1'), ('type1');
INSERT INTO user_tasks (type) VALUES ('type2'), ('type2'), ('type2'), ('type2'), ('type2');
INSERT INTO user_tasks (type) VALUES ('type3'), ('type3'), ('type3'), ('type3'), ('type3');
INSERT INTO user_tasks (type) VALUES ('type4'), ('type4'), ('type4'), ('type4'), ('type4');
INSERT INTO user_tasks (type) VALUES ('type5'), ('type5'), ('type5'), ('type5'), ('type5');
INSERT INTO user_tasks (type) VALUES ('type6'), ('type6'), ('type6'), ('type6'), ('type6');
INSERT INTO user_tasks (type) VALUES ('type7'), ('type7'), ('type7'), ('type7'), ('type7');
INSERT INTO user_tasks (type) VALUES ('type8'), ('type8'), ('type8'), ('type8'), ('type8');
INSERT INTO user_tasks (type) VALUES ('type9'), ('type9'), ('type9'), ('type9'), ('type9');
INSERT INTO user_tasks (type) VALUES ('type10'), ('type10'), ('type10'), ('type10'), ('type10');

CREATE TABLE

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

INSERT 0 5

id	type	rn
5	type1	1
4	type1	2
50	type10	1
49	type10	2
6	type2	1
7	type2	2
11	type3	1
12	type3	2
16	type4	1
20	type4	2
21	type5	1
22	type5	2
26	type6	1
27	type6	2
31	type7	1
32	type7	2
36	type8	1
37	type8	2
45	type9	1
44	type9	2

SELECT 20