List<Map<String, Object>> 对应 map 前端:[ ] SQL 的 AS 就是 key

   <select id="method" resultType="map">
   SELECT
   type AS Type,
   SUM( num ) AS totalNum 
   FROM
   aTable
   GROUP BY
   a
   </select>
   

返回格式

    [
    {Type:"XX",totalNum:"XXX"},
    {Type:"XX",totalNum:"XXX"},
    {Type:"XX",totalNum:"XXX"}
    ]

Map<String, Object> 对应 map 前端:{ } SQL 的 AS 就是 key

   <select id="method" resultType="map">
   SELECT
   type AS Type,
   SUM( num ) AS totalNum 
   FROM
   aTable
   GROUP BY
   a
   </select>
   

返回格式

    {Type:"XX",totalNum:"XXX"}

带WHERE参数 resultType="map" parameterType="String" parameterType 最好显示定义 不然会有莫名其妙的报错[可选]