How to Handle Dynamically Sized Parameter Lists in MySQL Prepared Statements?

Dynamically Sized Parameter Lists in MySQL Prepared Statements

When constructing MySQL prepared statements in PHP, the question of how to handle queries with a variable number of arguments arises. For instance, consider a query like this:

SELECT `age`, `name` FROM `people` WHERE id IN (12, 45, 65, 33)

The number of IDs in the IN clause varies with each execution.

Possible Solutions

Various approaches exist to address this challenge:

1. Solution 1: Dummy Variables and Multiple Calls

   • Create a statement that accepts a fixed number of variables (e.g. 100) and fill unused slots with dummy values.
   • Execute multiple calls for larger sets.

2. Solution 2: Non-Prepared Query

   • Build the query dynamically and execute it, ensuring stringent protection against injection attacks.

Optimal Solution

However, other options offer better efficiency:

1. Temporary Table Approach

   • Create a temporary table and insert each parameter value into it.
   • Perform a simple join against the temporary table.

2. Dynamic IN Clause

   • Construct the query dynamically with a placeholder for the IN clause using implode and array prefill functions.

   • For example:

     $dbh = new PDO(...);
     $parms = [12, 45, 65, 33];
     $inclause = implode(',', array_fill(0, count($parms), '?')); // = ?,?,?,?
     $preparesql = sprintf('SELECT age, name FROM people WHERE id IN (%s)', $inclause);
     $st = $dbh->prepare($preparesql);
     $st->execute($parms);

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The first approach may be more efficient for large sets, while the second is suitable for smaller ones.

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