How Can I Use Variables with MySQL's LIMIT Clause?

How to Utilize Variables in MySQL LIMIT Clauses

In MySQL, utilizing variables in LIMIT clauses can present a challenge when working with stored procedures involving integer input parameters like 'my_size.' The native implementation doesn't directly support this functionality. However, there are several routes to circumvent this limitation.

Utilizing Subqueries

If MySQL versions earlier than 5.5.6 are being utilized, or if stored procedures are not desired, a subquery with a WHERE clause and ROWNUM can serve as an effective solution.

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

Dynamic Query Preparation

Another approach involves constructing the query dynamically using string concatenation, assigning the result to a variable, and then executing the prepared query.

SET @query = 'SELECT * FROM some_table LIMIT ' || my_size;
PREPARE stmt FROM @query;
EXECUTE stmt;

Employing Prepared Statements

Alternatively, prepared statements offer a method to pass parameters to dynamic SQL statements, including the LIMIT clause.

SET @limit = 10;
PREPARE stmt FROM 'SELECT * FROM some_table LIMIT ?';
SET @param = @limit;
EXECUTE stmt USING @param;

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