Comment by mrweasel

You kinda have to. Assuming that you're using an ORM, you still need to understand how it translate to SQL, and help it do the translation correctly.

Personally I've seen developer use the Django ORM, and create application with terrible performance. Tweaking the queries, you can help guide the ORM to generate better SQL, which in turn will affect your performance greatly.

We're currently facing a problem with a custom who have an application with terrible performance/scaling issues. The entire thing is very database heavy, but interaction is done solely via Hibernate. I have nothing against Hibernate, it's a fine ORM, but you need to understand it well enough that you can guide it towards better queries (Which sometimes involve actually writing SQL). At some point you need to decide if your time isn't better spend learning SQL directly, as that via always provide you with better access to the functionality provided by the database.