Is there a way using either the Zen admin panel or a MySQL command to globally set all product quantities to zero?

I've been using EZP and uploading daily price/quantity updates from my supplier, but the problem for me is that because of how I set up my store, when they no longer carry an item, I don't know, it stays in my database, and I've had customers order items that I can't fulfill.

If I can set all items to zero, then upload a new price/quantity file, then the items that are discontinued will be zero and unorderable, the others will carry on as normal.

Thanks in advance!