例子:

sql两个字段排序

      ORDER  BY   update_time  DESC , create_time  DESC

    <select id="selectLawIllegalActivitiesList" parameterType="LawIllegalActivities" resultMap="LawIllegalActivitiesResult"><include refid="selectLawIllegalActivitiesVo"/><where>  <if test="illegalActivities != null  and illegalActivities != ''"> and illegal_activities like concat('%', #{illegalActivities}, '%')</if><if test="terms != null  and terms != ''"> and terms = #{terms}</if><if test="termsContent != null  and termsContent != ''"> and terms_content = #{termsContent}</if><if test="according != null  and according != ''"> and according = #{according}</if><if test="accordingContent != null  and accordingContent != ''"> and according_content = #{accordingContent}</if></where>ORDER  BY   update_time  DESC , create_time  DESC</select>

  /*** 查询违法事项库列表* * @param lawIllegalActivities 违法事项库* @return 违法事项库集合*/public List<LawIllegalActivities> selectLawIllegalActivitiesList(LawIllegalActivities lawIllegalActivities);

如果新增数据 只有创建时间 没有更新时间  想要新增数据排到最前面

ORDER BY 
  COALESCE(update_time, create_time) DESC,
  create_time DESC
 

这里使用了COALESCE函数，它会返回第一个非空参数的值。如果update_time是NULL，则COALESCE(update_time, create_time)将使用create_time的值进行排序。这样，无论是否有更新时间，所有记录都会按照最新的时间戳进行降序排列。

  <select id="selectLawIllegalActivitiesList" parameterType="LawIllegalActivities" resultMap="LawIllegalActivitiesResult"><include refid="selectLawIllegalActivitiesVo"/><where>  <if test="illegalActivities != null  and illegalActivities != ''"> and illegal_activities like concat('%', #{illegalActivities}, '%')</if><if test="terms != null  and terms != ''"> and terms = #{terms}</if><if test="termsContent != null  and termsContent != ''"> and terms_content = #{termsContent}</if><if test="according != null  and according != ''"> and according = #{according}</if><if test="accordingContent != null  and accordingContent != ''"> and according_content = #{accordingContent}</if></where>ORDER BYCOALESCE(update_time, create_time) DESC,create_time DESC</select>