mybatis 批量更新数据

int updateBatch(@Param("entities") List<Drug> entities);

<update id="updateBatch" parameterType="java.util.List">

    UPDATE drug SET

　　 num = CASE

    <foreach collection="entities" item="item" index="index" open="" close="" separator=" ">

        WHEN id = #{item.id}

            <if test="item.operNum != null and item.operNum != ''">

                THEN num + #{item.operNum}

            </if>

            <if test="item.operNum == null or item.operNum == ''">

                THEN num

            </if>

    </foreach>

    END,

    update_time = CURRENT_TIMESTAMP

    WHERE id IN

    <foreach collection="entities" item="item" index="index" open="(" close=")" separator=",">

        #{item.id}

    </foreach>

</update>