Website freeze on entering Query

[pagdot]

When entering this Query

UPDATE entries SET category=( SELECT S.nr FROM categories C, subcategories S WHERE (C.name="Transport") AND (S.name="Öffentlich") AND (C.nr=S.catNr) ) WHERE nr = 1

the webapp freezes

It happens when entering the text or pasting it into the text field. Tested on Chrome and Firefox