MySQL IF EXISTS not working

Trying to use IF EXISTS to automatically choose which table to select a record from.

I just get the following error message with the code below.

Where am I going wrong?

IF EXISTS (SELECT 1 FROM Users WHERE Reference='USR00000007')
    SELECT * FROM Users WHERE Reference='USR00000007'
ELSE
    SELECT * FROM Staff WHERE Reference='USR00000007';

Error: #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 'IF EXISTS (SELECT 1 FROM Users WHERE Reference='USR00000007') SELECT * FROM' at line 1