How I Make Result Of Sql Querys With Limit Different In Each Query?

I have the following SQL: SELECT id, url FROM link WHERE visited = false ORDER BY id LIMIT 500; --*500 is only a example I'm making a webcrawler and there is a table with li

Solution 1:

Have you tried for update/returning?

update link
set visiting =truefrom (
    select id
    from link
    where visiting =falseand visited =false
    limit 500forupdate
    ) as batch
where batch.id = link.id
returning *;

Solution 2:

Skip 1500 rows and take the next 500

SELECT id, url 
FROM link 
WHERE visited =falseORDERBY id 
LIMIT 500OFFSET1500

http://www.postgresql.org/docs/8.3/interactive/queries-limit.html