Mybatis使用的问题

[liudachu]

mapper

<!--批量添加上架商品-->
    <insert id="insertMultiGis" parameterType="java.util.List"  useGeneratedKeys="true" keyProperty="gis_id" keyColumn="gis_id">
        INSERT INTO goodinstore
        (goodid,businessid,retailprice,min_stock,stock)
        values
        <foreach collection="list" item="item" index="index" separator=",">
         (#{item.good.id},#{item.businessid},#{item.retailPrice},#{item.min_stock},#{item.stock})
        </foreach>
        ON DUPLICATE KEY UPDATE
        retailprice = values(retailprice),
        min_stock = values(min_stock),
        stock = values(stock)
    </insert>

其中下方代码的含义用途是什么？

 ON DUPLICATE KEY UPDATE
        retailprice = values(retailprice),
        min_stock = values(min_stock),
        stock = values(stock)

[街头小贩]

若存在记录(唯一约束)。则更新retailprice ,min_stock ,stock