Oracle中sql有则修改无则添加

例如，demo表中有name,price,nowtime等字段，需要根据name字段进行判断，存在则修改，不存在则添加
<update id="updateshoppings" parameterType="String">
    MERGE INTO demo t1
    USING(SELECT #{name} name,#{price}  price,#{nowtime} nowtime FROM dual) t2
    ON(t1.name=t2.name)
    WHEN MATCHED THEN
    update set t1.price=t2.price,t1.nowtime=t2.nowtime
    WHEN NOT MATCHED THEN
    insert(name,price,nowtime) VALUES(t2.name,t2.price,t2.nowtime)
</update>