How to Properly Bind Array Values to a MySQL IN Statement Using PDO?

PDO Binding Values for MySQL IN Statement

You're facing an issue when using PDO to bind an array of values to a MySQL IN statement. Your goal is to execute the query as follows:

SELECT users.id
FROM users
JOIN products
ON products.user_id = users.id
WHERE products IN (1,2,3,4,5,6,7,8)

However, PDO is converting the bound values into a comma-separated string, resulting in the following erroneous query:

SELECT users.id
FROM users
JOIN products
ON products.user_id = users.id
WHERE products IN ('1,2,3,4,5,6,7,8')

You've tried using a custom function to split the comma-separated string inside the query itself, but this isn't an optimal solution.

Solution 1: Constructing the Query Manually

As suggested in a previous question, you can manually construct the query by concatenating the placeholders for each IN clause value. For example:

$products = array(1,2,3,4,5,6,7,8);
$placeholders = array_fill(0, count($products), '?');
$sql = "SELECT users.id
FROM users
JOIN products
ON products.user_id = users.id
WHERE products IN (" . implode(',', $placeholders) . ")";
$stmt = $pdo->prepare($sql);
$stmt->execute($products);

Solution 2: Using find_in_set()

You can use the find_in_set() function to match a value against a comma-separated string. However, this approach may have performance issues with large datasets, as it requires converting every value in the table to a character type.

$products = array(1,2,3,4,5,6,7,8);
$sql = "SELECT users.id
FROM users
JOIN products
ON products.user_id = users.id
WHERE find_in_set(cast(products.id as char), '" . implode(',', $products) . "') > 0";
$stmt = $pdo->prepare($sql);
$stmt->execute();

Solution 3: Creating a User Defined Function

The best solution is to create a user defined function (UDF) that splits the comma-separated string. This is a relatively complex solution, but it provides the best performance for IN clauses with variable-sized lists.

Refer to the provided link for instructions on creating the UDF.

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