DELETE
FROM m_productprice B
USING m_product C
WHERE B.m_product_id = C.m_product_id AND
C.upc="7094" AND
B.m_pricelist_version_id='1000020';
or
DELETE
FROM m_productprice
WHERE m_pricelist_version_id='1000020' AND
m_product_id IN (SELECT m_product_id
FROM m_product
WHERE upc="7094");