MySQL parser errors

Hi, I've found a MySQL script parse error (IN statement) without any warnig sent to user. Here is the evidence.

Write down any select statement with condition in a list. E.G.:

SELECT FROM progetti p WHERE p.struttura=392 AND p.numproj in ( '20C120', '20C91', '20C92', '20C93' ); / Affected rows: 0 Found rows: 4 Warnings: 0 Duration for 1 query: 0,125 sec. */

This is correct, but now rwrite down the same query and intentionally do not use ',' between elements in list:

SELECT FROM progetti p WHERE p.struttura=392 AND p.numproj in ( '20C120' '20C91' '20C92' '20C93' ); / Affected rows: 0 Found rows: 0 Warnings: 0 Duration for 1 query: 0,125 sec. */

Query executed without any warning... Forgetting ',' could potentially lead user to think errouneusly that query is correct and there are no results at all.

Best regards.