Using Limit on Distinct group by values psql - sql

Question

Suppose I have a table that looks like this or maybe I am going nowhere.
create table customers (id text, name text, number int, useless text);
With values
insert into customers (id, name, number, useless)
values
('1','apple',1, 'a'),
('2','banana',3, 'b'),
('3','pear',2, 's'),
('4','apple',1,'e'),
('5','banana',3,'s'),
('6','cherry',3, 'a'),
('7','cherry',4, 's'),
('8','apple',2, 'd'),
('9','banana',4, 'c'),
('10','pear',5, 'e');
My failed psql query is this.
select id, name, number, useless
from customers
where number < 4
group by customers.name limit 2
the query i want to use that it returns first 2 unique grouped by customers.name. Not the first 2 rows
In the end I want it to return
('1','apple',1, 'a'),
('4','apple',1,'e'),
('8','apple',2, 'd'),
('2','banana',3, 'b'),
('5','banana',3,'s'),
so it returns the first 2 grouped names.
How can I make this query?
Thank you.
Edit:
this query is my second try I know I am kinda close.
select t.id, t.name, t.ranking
from (
SELECT id, name, dense_rank() OVER (order by name) as
ranking
FROM customers
group by name
) t
where t.ranking < 3

Answer 1

try this:
select id, name, number, useless
from customers
where name in (
select name
from customers
where number < 4
group by customers.name
order by name limit 2
)
| id | name | number | useless |
|----|--------|--------|---------|
| 1 | apple | 1 | a |
| 2 | banana | 3 | b |
| 4 | apple | 1 | e |
| 5 | banana | 3 | s |
| 8 | apple | 2 | d |
| 9 | banana | 4 | c |
SQL Fiddle DEMO

Answer 2

The group by customers.name function do not order your output, just group them by the customers.name, what you want to do is to order the group right? So what i think you want to do is:
select id, name, number, useless
from customers
group by name
order by name []*
*[asc/desc] depends of what order you want to do:
asc - ascendent,
desc - descendent
Hope it helps you.

Answer 3

You can use dense_rank() as:
SELECT * FROM (
SELECT DENSE_RANK() OVER (order by name) AS rank, temp.*
FROM customers temp WHERE number < 4) data
WHERE data.rank <= 2
| rank| id| name | number | useless |
|-----|---|--------|--------|---------|
| 1 | 4 | apple | 1 | e |
| 1 | 1 | apple | 1 | a |
| 1 | 8 | apple | 2 | d |
| 2 | 5 | banana | 3 | s |
| 2 | 2 | banana | 3 | b |