DB Query UPDATE problems

Hi,
I'm editing some columns in amember's db.
I have to do this query:

UPDATE am_invoice
SET "first_subtotal"=1
WHERE "first_subtotal"=0.93;

But MySQL tell me this: "#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'FROM am_invoice WHERE first_subtotal = 0 , 93' at line 2"

How can I do that?

Thank you in andvance and sorry for my english


UPDATE: SOLVED. The correct query is this:

UPDATE am_invoice
SET first_subtotal=1
WHERE first_subtotal=0.93