Using variable in a LIMIT clause in MySQL

A search turned up this article. I've pasted the relevant text below.

Here's a forum post showing an example of prepared statements letting you assign a variable value to the limit clause:

http://forums.mysql.com/read.php?98,126379,133966#msg-133966

However, I think this bug should get some attention because I can't imagine that prepared statements within a procedure will allow for any procedure-compile-time optimizations. I have a feeling that prepared statements are compiled and executed at the runtime of the procedure, which probaby has a negative impact on efficiency. If the limit clause could accept normal procedure variables (say, a procedure argument), then the database could still perform compile-time optimizations on the rest of the query, within the procedure. This would likely yield faster execution of the procedure. I'm no expert though.

STORED PROCEDURE

DELIMITER $
CREATE PROCEDURE get_users(page_from INT, page_size INT)
BEGIN
  SET @_page_from = page_from;
  SET @_page_size = page_size;
  PREPARE stmt FROM "select u.user_id, u.firstname, u.lastname from users u limit ?, ?;";
  EXECUTE stmt USING @_page_from, @_page_size;
  DEALLOCATE PREPARE stmt;
END$

DELIMITER ;

USAGE

In the following example it retrieves 10 records each time by providing start as 1 and 11. 1 and 11 could be your page number received as GET/POST parameter from pagination.

call get_users(1, 10);
call get_users(11, 10);

For those, who cannot use MySQL 5.5.6+ and don't want to write a stored procedure, there is another variant. We can add where clause on a subselect with ROWNUM.

SET @limit = 10;
SELECT * FROM (
  SELECT instances.*, 
         @rownum := @rownum + 1 AS rank
    FROM instances, 
         (SELECT @rownum := 0) r
) d WHERE rank < @limit;