Use following query to update the customer password in magento2.
UPDATE customer_entity SET password_hash = CONCAT(SHA2('xxxxxxxxNewPassword', 256),':xxxxxxxx:1') WHERE entity_id = customerid;
xxxxxxxx : replace with any of your alphanumeric string both places should use same.
entity_id: obtian customer id from magento url
Newpassword: alphanumeric value 9 in total