Jenke mybatis特殊sql

1、多参数虚拟表批量查询

<select id="getProductUnitPriceList" parameterType="java.util.Map" resultType="String">          select ifnull(product_unit_price,"") 'product_unit_price'        from t_product b right join (        <foreach collection="list" index="index" item="item" separator="union all">select #{item} product_keyword from dual        </foreach>) a on a.product_keyword = b.product_keyword    </select>  

mysql 的数据库，期中 union all不 会去重复，要去重复改union