Question

with this code I select the first 30 row of the table:

SELECT * FROM `table` LIMIT 0 , 30

But how to select the last 30, without changing the order?

Answer 1

It looks like everyone is missing this part:

But how to select the last 30, without changing the order?

First of all, clearly there is no order in the query provided. Assuming the order is ascending on some field this would be the query @DannyFox meant:

SELECT * FROM T
ORDER BY val
LIMIT 0 , 30

Now imagine we have simplified data, such as a, b, c, d, e and that we want only 3 rows instead of 30:

SELECT * FROM T
ORDER BY val
LIMIT 3

If this returns: a, b, c, d, e in each row, then he would expect to get c, d, e in that order. The query everyone is providing:

SELECT * FROM T
ORDER BY val desc
LIMIT 3

Would return e, d, c. The problem with this is that it’s actually changing the original order, and the OP say he didn’t want to change the order. So technically, the query that would result in c, d, e is:

select * from (
  select * from t
  order by val desc
  limit 3
) s
order by val

Which actually changes the order twice, getting the original order back.