这是一个子查询

SELECT a.* from i as  a
inner join (
select max(datetime) as datetime,asset_name,max(asset_code) as asset_code
FROM i
<if test="taskId != null and taskId!=''">
    WHERE taskid = #{taskId}
</if>
<if test="type != null and type!=''">
    and inout_status = #{type}
</if>

GROUP BY asset_name
) b
on a.asset_code = b.asset_code and a.datetime = b.datetime

<if test="inoutStatus != null and inoutStatus!=''">
    and inout_status = #{inoutStatus}
</if>
ORDER BY dateTime DESC

这是一个字符串循环查询比如接受字符串是   张三,李四

<select id="selectIdByLocation" resultType="java.lang.String" >
    select dev_id from door_dev_antenna
    where door_name in
    <foreach item="item" index="index" collection="location.split(',')"  open="(" separator="," close=")">
        #{item}
    </foreach>
</select>

location就是  张三,李四