在bean中，count是long型別：

private Long count;

需求就是利用下面的更新語句更新bills表中的count和amout

<update id="updateBills" parameterType="map" >
  UPDATE bills 
  <set>
  <if test="count != null and count != ''">
     count = #{count,jdbcType=NUMERIC},
  </if>
  <if test="amount != null and amount != ''"
 
>
     amount = #{amount,jdbcType=NUMERIC},
  </if>
            update_time = now() 
</set> 
    where id = #{id,jdbcType=VARCHAR} 
    and 
    bill_date = to_date(#{billDate,jdbcType=DATE},'yyyy-MM-dd'))
</update>

問題出現了：

Map<Object, Object> updateMap = new HashMap<Object, Object>();
 

updateMap .put("id", bills.getId());
updateMap .put("billDate",dateString);
updateMap .put("amount", bills.getAmount());
updateMap .put("count",bills.getCount());

billsDao.updateBills(updateMap);

當bills.getCount()等於0時，就是無法更新，所以我不得不做了以下判斷，然後就有效的解決了這個問題，但是因為什麼呢？我也不知道！

Map<Object, Object> updateMap = new HashMap<Object, Object>();
 

updateMap .put("id", bills.getId());
updateMap .put("billDate",dateString);
updateMap .put("amount", bills.getAmount());
if(0 == bills.getHisCount()){
    updateMap .put("count",0);
}else{
    updateMap .put("count",bills.getCount());
}
billsDao.updateBills(updateMap);