一、根据id更新多个字段

    <update id="batchUpdate">
        update food
        <trim prefix="set" suffixOverrides=",">
            <trim prefix="open_id =case" suffix="end,">
                <foreach collection="list" item="item" index="index">
                    when id=#{item.id} then #{item.openId}
                </foreach>
            </trim>
            <trim prefix="create_by =case" suffix="end,">
                <foreach collection="list" item="item" index="index">
                    when id=#{item.id} then #{item.createBy}
                </foreach>
            </trim>
        </trim>
        where id in
        <foreach collection="list" index="index" item="item"
                 separator="," open="(" close=")">
            #{item.id}
        </foreach>
    </update>