Max(datetime_column) in a where clause - mysql

Question

I created a query to update a field. But I need to change the value of the last record. In my ps_order_history table there's the date_add column. Its type is datetime. How could I get the last record if I can't use the max() function in where clause? This is what I got until now (there's some fixed parameters, but it's just to test. I'll change this in the PHP code):
UPDATE ps_order_history AS h
INNER JOIN ps_order_detail d ON d.id_order = h.id_order
INNER JOIN ps_orders o ON o.id_order = h.id_order
SET h.id_order_state = 18
WHERE d.product_name = "Academia Mastermaq"
AND o.id_customer = (
SELECT id_customer
FROM ps_customer
WHERE firstname = "Cristiano"
AND lastname = "Ferreira dos Santos"
)
AND max(h.date_add)
Thanks.

Answer 1

you can do that by using Order by xxx DESC LIMIT 1

Answer 2

Got it! I've discovered about variables in MySQL and used a one to store the max id_order_history (I realized I didn't need the date_add column because the max id_order_history is the last data). After, I updated the table.
This is the query:
SET #maxid =
(
SELECT max(h.id_order_history)
FROM ps_order_history h
WHERE h.id_order =
(
SELECT max(p.id_order)
FROM ps_orders p
INNER JOIN ps_order_detail d ON d.id_order = p.id_order
WHERE p.id_customer =
(
SELECT id_customer
FROM ps_customer
WHERE firstname = '$firstname'
AND lastname = '$lastname'
LIMIT 1
)
AND d.product_name = '$nome_produto'
AND p.module = 'pagseguro'
LIMIT 1
)
);
UPDATE ps_order_history h
SET h.id_order_state = $status
WHERE h.id_order_history = #maxid;