Mybatis choose when用法实例代码

<select id="query" resultType="map" parameterType="map">    select       <choose>        <when test="cityId == '00' ">            a.city_id as CITYID,        </when>        <otherwise>          <choose>            <when test="cityId == '0001' and statsDimension==1">              a.level1_maintain_unit_id as CITYID,            </when>            <otherwise>              a.county_id as CITYID,            </otherwise>          </choose>         </otherwise>     </choose>          sum(ONUNUM) as ONUNUM,           sum(ONTNUM) as ONTNUM      from new_olt_upopt_sp_month_${tableDate} a      where 1 = 1        <if test="cityId == '0001' and statsDimension==1">        and a.city_id = '0001'        </if>        <![CDATA[and a.gather_time >= ${startDate}]]>        <![CDATA[and a.gather_time <= ${endDate}]]>           group by    <choose>        <when test="cityId == '00' ">            a.city_id        </when>        <otherwise>          <choose>            <when test="cityId == '0001' and statsDimension==1">              a.level1_maintain_unit_id            </when>            <otherwise>              a.county_id              having a.county_id in                 (select city_id from tab_city                   where city_id= #{cityId} or parent_id=#{cityId})            </otherwise>          </choose>         </otherwise>     </choose>        </select>