Syntax error in SELECT query inside PHP script - php

Question

I am trying to create a query inside a PDO script that checks if a record exists if it does the query should update the record and if it doesn't exist it should create a new one.
The column that should only exist once in the table is not an INDEX key (cannot make it unique right now) so it is not set as unique and I cannot use the ON DUPLICATE KEY UPDATE
I would like to use this queries logic below to make it work:
$stmt = $conn->prepare('IF EXISTS (SELECT * FROM `Table1` WHERE `code`= :code )
UPDATE `Table1`
SET `code_stat` = 2
WHERE code = :code
ELSE
INSERT INTO `Table1` (`code`,`code_stat`)
VALUES (:code, 2 ) ' );
$stmt->execute([
'code' => $_POST['code']
]);
The problem is when executing the query I get the following error saying there is a syntax problem:
SQL syntax; check the manual that corresponds
to your MySQL server version for the right syntax to use near
'IF EXISTS (SELECT * FROM Table1 WHERE code= ? ) UPDATE Table1' at line 1

Answer 1

If you can't add a unique key to the table, you can attempt an update first, and if that doesn't update any rows, do an insert. Something like this:
$stmt = $conn->prepare('UPDATE `Table1` SET `code_stat` = 2 WHERE code = :code');
$stmt->execute(array(':code' => $_POST['code']));
if (!$stmt->rowCount()) {
// no rows updated, so insert
$stmt = $conn->prepare('INSERT INTO `Table1` (`code_stat`, `code`) VALUES (2, :code)');
$stmt->execute(array(':code' => $_POST['code']));
}
Note that you may need to set the PDO::MYSQL_ATTR_FOUND_ROWS attribute to ensure that the UPDATE query returns 1 if it finds the row but the value doesn't change. You must set that attribute when you make the connection e.g.
$conn = new PDO($dsn, $user, $pass, array(PDO::MYSQL_ATTR_FOUND_ROWS => true));

Answer 2

Why not write a stored procedure to handle this, similar to the below:
DROP PROCEDURE IF EXISTS db.SP_NEW_CODE;
CREATE PROCEDURE db.`SP_NEW_CODE`(IN `in_code` INT)
BEGIN
DECLARE numFound INT DEFAULT 0;
SET numFound=(SELECT * FROM `Table1` WHERE `code`= in_code);
IF (numFound=0) THEN
INSERT INTO `Table1` (`code`,`code_stat`) VALUES (in_code, 2 );
ELSE
UPDATE `Table1` SET `code_stat` = 2 WHERE code = in_code
END IF;
END;
From your code, simple execute CALL SP_NEWCODE(3); (for example, where 3 is the appropriate code value).