Is there a way to use variables in conjunction with the SQL LIMIT clause?
(e.g. SELECT * FROM movies LIMIT @foo)?
No not directly…at the time of writing this is still a big issue of MySQL Development. Nonetheless there exist various workarounds. I will discuss a few of them in this article.
The main issue is that you want to construct an SQL query that hands a variable as a parameter to the LIMIT clause. That could look something like this:
SET @foo = 5; SELECT * FROM movies LIMIT @foo;
This immediately results in the following error message.
Error Code: 1064
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘@’ at line 1)
So to all appearances SELECT queries using the LIMIT clause do not work when a SQL variable (e.g. @foo) is used as a parameter in the LIMIT clause.
In the following I present a few workarounds to resolve this little handicap:
1. Make use of Prepared Statements
SET @foo=5; PREPARE STMT FROM 'SELECT * FROM table LIMIT ?'; EXECUTE STMT USING @foo;
You could also concatenate your entire SELECT Statement and convert this to a Prepared Statement. In the following example the parameter “sParameter” is the used variable.
SET @myQuery = CONCAT('SELECT * FROM test ORDER BY ', sParameter); PREPARE stmt FROM @myQuery; EXECUTE stmt; DEALLOCATE PREPARE stmt;
If you use queries like these a lot, it might make sense to wrap the whole thing up in a stored procedure:
DELIMITER $$ CREATE PROCEDURE `get_movie_range`( IN _FROM INTEGER, IN _TO INTEGER ) BEGIN PREPARE STMT FROM "SELECT * FROM movies LIMIT ?,? "; SET @FROM = _FROM; SET @TO = _TO; EXECUTE STMT USING @FROM, @TO; END$$
With the stored procedure in place you can make calls like:
CALL get_movie_range(7,(SELECT COUNT(*) FROM movies));
2. Make use of variables and the BETWEEN Statement
This statement selects all rows beginning with 12 and ending at 20.
set @i=0; select * from movies where (@i:=@i+1) between 12 and 20;
So that’s it…hope it helps…:)