Question

我想在现有的查询中添加2个新列。在第一个中，在当前行和下一行之间进行差异，在下一行中进行差异计算行之间的值。

我目前的查询是：

SELECT *, SUM(MINUTE(rest_time)) AS Times
  FROM routes as routes 
  LEFT JOIN sales
    ON (routes.departure_poi_code = sales.client_code AND
        routes.departure_date = sales.`date`)
 WHERE (routes.departure_poi_code LIKE 'C0%' OR routes.departure_poi_code LIKE 'MP%')
   AND routes.`car_no` =  'BH-07-EWR'
   AND routes.departure_date =  '2011-10-14'
 GROUP BY routes.departure_address, reports.routes.departure_poi_code,
          reports.routes.car_no, reports.routes.departure_date
 ORDER BY routes.car_no
 LIMIT 500000

我当前查询的结果如下：

Car_Numbr   Str_time    Cod_nr  KM
BH-07-EWR   08:59:00    C00425  7000
BH-07-EWR   10:29:00    C00149  8500
BH-07-EWR   14:27:00    C01075  9200
BH-07-EWR   15:07:00    C00305  9800
BH-07-EWR   16:08:00    C02572  9900

当然它包含更多列，但在此处显示所有列无关紧要。

故事是一辆汽车从客户1到客户2进行了行.2km-row1.km。当然，汽车km是它在船上的。我希望它是：

Car_Number  Start_time  Code_nr KM  Total_km        Diff_km 
BH-07-EWR   08:59:00    C00425  7000    0   (km counter starting from 0)    0       (first row show have 0)
BH-07-EWR   10:29:00    C00149  8500    1500    (0+8500-7000)   1500    (8500-7000)
BH-07-EWR   14:27:00    C01075  9200    2200    (upper result+9200-8500)    700    (9200-8500)
BH-07-EWR   15:07:00    C00305  9800    2800    (upper result+9800-9200)    600 (9800-9200)
BH-07-EWR   16:08:00    C02572  9900    2900    (upper result+9900-9800)    100 (9900-9800)

我怎样才能以最简单的方式实现这一目标？

Answer 1

将结果存储到临时表（CREATE TEMPORARY TABLE ... SELECT ...）中，然后使用此查询计算值 -

SELECT
  c.*,
  @diff:=IF(@prev_km IS NULL, 0, km - @prev_km) diff_km,
  @prev_diff_km:=IF(@prev_diff_km IS NULL, 0, @prev_diff_km + @diff) total,
  @prev_km:=km
FROM
  car_temp c,
  (SELECT @prev_km := NULL, @prev_diff_km:=NULL) t

行之间的差异

1 个答案: