Why Does My Multiple Insert Query Return 'Invalid Parameter Number'?

Error: Invalid Parameter Number in Multiple Insert Query

When attempting to insert multiple records into a database table, you may encounter the "Invalid parameter number: parameter was not defined" error. This occurs when the number of parameters specified in the query does not match the number of values provided as input.

Understanding the Issue

In the provided code snippet:

$matches = array('1');
$count = count($matches);
for($i = 0; $i < $count; ++$i) {
    $values[] = '(?)';
}

// Build query
$q = $this->dbc->prepare("INSERT INTO hashes (hash) VALUES " . implode(', ', $values) . " ON DUPLICATE KEY UPDATE hash = hash");
$q->execute($matches);

The goal is to insert the value in $matches into the hashes table, using a prepared statement. However, the error occurs because the number of placeholder parameters (?) in the $values array does not correspond to the actual data in $matches.

Fix

To resolve this issue, ensure the following:

1. Initialize arrays: Always initialize the $values array before the loop to avoid preexisting values.
2. Confirm data count: Verify that the number of elements in $values is equal to the number of elements in $matches. If not, adjust the loop or add conditional checks.
3. Create unique index: Check if the hash column has a unique index. This prevents duplicate entries and ensures that each provided value is inserted or updated.
4. Use parameterized statement: Employ a prepared statement to prevent SQL injection and parameter binding issues.

Example

$matches = array('1');
$values = [];
$count = count($matches);

for($i = 0; $i < $count; ++$i) {
    $values[] = '(?)';
}

// Insert query with named parameters (:hash)
$sql = "INSERT INTO hashes (hash) VALUES (:hash) ON DUPLICATE KEY UPDATE hash = VALUES(:hash)";
$stmt = $dbh->prepare($sql);
$data = $stmt->execute([':hash' => $matches]);

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