MYSQL Insert Where Not Exists with PDO

Question

I am conditionally inserting values to a MySQL database using a PHP PDO command. The condition states that if the row to be inserted already exists, do not insert it. If it do

Answer 1

Your query looks completely messed up, especially in your EXISTS sub-query. You're selecting MyTbl.ColA from tickets???

My advice would be to simply add a unique constraint on MyTbl (ColA, ColB).

ALTER TABLE MyTbl ADD UNIQUE (ColA, ColB);

Then, your INSERT will fail with a unique constraint violation which can be caught in a PDOException.

$stmt = $pdo->prepare('INSERT INTO MyTbl (ColA, ColB) VALUES (?, ?)');
foreach ($loopme as $foo) {
    try {
        $stmt->execute([$foo->fooA, $foo->fooB]);
    } catch (PDOException $e) {
        $errorCode = $stmt->errorInfo()[1];
        if ($errorCode == 1586) {
            // I think 1586 is the unique constraint violation error.
            // Trial and error will confirm :)
        } else {
            throw $e;
        }
    }
}

To address the error message you're seeing... it's because you aren't differentiating between the INSERT table and the sub-query table.