Code MySQL:
UPDATE ct 
		SET ct.site_id = su.site_id 
		FROM credit_transactions AS ct 
		JOIN site_user AS su ON ct.user_id = su.user_id

I get

#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 credit_transactions AS ct JOIN site_user AS su ON ct.user_id = su.user_' at line 3
Ive looked all over google and it seems my syntax is correct :/