SQL Transaction ELSE IF with SELECT - mysql

Question

I am trying to create a query, that will check if it exist in a table, if it exist, it will just add one to quantity qty else it will insert from a selecting from other table, in my case temp_sales
here's my sql so far.
SET
TRANSACTION ISOLATION LEVEL SERIALIZABLE; BEGIN TRANSACTION; IF EXISTS (
SELECT
pid
FROM
temp_sales
WHERE
barcode = '4800556410652'
) BEGIN
UPDATE
temp_sales
SET
qty = qty + 1
WHERE
barcode = '4800556410652' END ELSE INSERT INTO temp_sales (
0,
(
SELECT
products.ID,
products.product_sprice as price,
1,
1 * price,
'4800556410652',
'101',
'admin'
WHERE
barcode = '4800556410652'
)
) END COMMIT TRANSACTION;
I have been following this stackoverflow answer from UPDATE if exists else INSERT in SQL Server 2008 but I have no luck.
MySQL error #104 #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 'TRANSACTION' at line 1
what did I do wrong?
EDIT
PL: vb.net
DB: MySQL(xampp)

Answer 1

Thanks for the comments, my bad. I was following a SQL server query instead of focusing on MySQL query.
But here's the answer after a few additional searches (of course with the help of the commentators) - thanks
Answer:
INSERT into temp_sales (
ID, pid, price, qty, total, barcode,
pos_id, teller
)
SELECT
'0',
ID as pid,
products.product_sprice,
1,
products.product_sprice,
#barcode,
'101',
'admin'
FROM
products
WHERE
barcode = #barcode ON DUPLICATE KEY
UPDATE
qty = qty + 1,
total = price * qty