利用mybatis 動態查詢一條記錄，而返回是一個map（resultType=”java.util.Map”，鍵是欄位名，值是欄位值），比如操作資料庫是通過儲存過程或者是直接傳一個String sql="select * from emp where e_id=1"字串來返回一個map。

1、如果某一列的值為空。查詢這條記錄時就不顯示這列了。《===map中無此對應的鍵

2、如果這個列是number型別，不能給預設值（比如 ‘0’）。只能為空，這樣也會顯示不出來《===map中無此對應的鍵

解決辦法：可以利用Oracle的nvl（）函式，比如nvl（欄位，’0’）表示如果欄位為空，則用0字元替代

<select id="queryLogonData" parameterType="java.util.Map" resultType="java.util.Map">
select nvl(aa.DEVICE_CNT,0) DEVICE_CNT, nvl(aa.EVENT_CNT,0) EVENT_CNT, nvl(aa.USER_CNT,0) USER_CNT,
    bb.CAL_NUMBER from
    (select 0 as DEVICE_CNT,sum(a.event_cnt) as EVENT_CNT,count(distinct(a.user_identifier)) as
    USER_CNT,a.CAL_NUMBER
    from razor_dw_user_logon_log_day a
    where 1 = 1
    <if 
 
test="version != 'all' and '' != version">
<![CDATA[
            AND VERSION =#{version}
            ]]>
    </if>
AND a.APP_KEY IN (SELECT PRODUCTKEY FROM RAZOR_CHANNEL_PRODUCT WHERE PRODUCT_ID = #{productId})
    AND a.cal_number between #{startTime} and #{endTime}
    group by a.cal_number
    order by a.cal_number ASC) aa
    right join dim_calendar bb
    on aa.cal_number = bb.cal_number
    where bb.cal_number between #{startTime} and #{endTime}
    order by bb.cal_number ASC
</select>