选择范围在最大值内的行

Question

I have the followng data:

+----+---------+---------------------+-------+
| id | site_id |      datetime       | views |
+----+---------+---------------------+-------+
|  1 |       1 | 2013-11-01 23:59:59 |    12 |
|  2 |       1 | 2013-11-02 23:59:59 |    15 |
|  3 |       1 | 2013-11-03 23:59:59 |    18 |
|  4 |       1 | 2013-11-04 23:59:59 |    29 |
|  5 |       1 | 2013-11-05 23:59:59 |    38 |
|  6 |       1 | 2013-11-05 12:59:59 |    40 |
|  7 |       1 | 2013-11-06 23:59:59 |    45 |
|  8 |       1 | 2013-11-07 23:59:59 |    49 |
|  9 |       1 | 2013-11-08 23:59:59 |    52 |
| 10 |       2 | 2013-11-04 23:59:59 |    25 |
| 11 |       2 | 2013-11-05 21:59:59 |    42 |
| 12 |       2 | 2013-11-06 23:59:59 |    60 |
| 13 |       2 | 2013-11-07 23:59:59 |    75 |
| 14 |       2 | 2013-11-08 23:59:59 |    86 |
| 15 |       2 | 2013-11-09 23:59:59 |    90 |
| 16 |       2 | 2013-11-10 23:59:59 |    92 |
| 17 |       2 | 2013-11-11 23:42:59 |    98 |
+----+---------+---------------------+-------+

I would pass a day and wish to get the rows with the highest time in the given day or if there`s no records for this site for this day, the last available row in the past.

eg for 2013-11-01

+----+---------+---------------------+-------+
| id | site_id |      datetime       | views |
+----+---------+---------------------+-------+
|  1 |       1 | 2013-11-01 23:59:59 |    12 |
+----+---------+---------------------+-------+

for 2013-11-05

+----+---------+---------------------+-------+
| id | site_id |      datetime       | views |
+----+---------+---------------------+-------+
|  5 |       1 | 2013-11-05 23:59:59 |    38 |
| 11 |       2 | 2013-11-05 21:59:59 |    42 |
+----+---------+---------------------+-------+

and for 2013-11-10

+----+---------+---------------------+-------+
| id | site_id |      datetime       | views |
+----+---------+---------------------+-------+
|  9 |       1 | 2013-11-08 23:59:59 |    52 |
| 16 |       2 | 2013-11-10 23:59:59 |    92 |
+----+---------+---------------------+-------+

Thanks in advance.

Answer 1

You can try this:

SELECT a.id,a.site_id,b.maxDate,a.views
FROM table1 a
INNER JOIN (
    SELECT  site_id ,MAX(datetime) as maxDate
    FROM table1
    WHERE datetime < DATEYOUWANTTOSEE + INTERVAL 1 DAY
    GROUP BY site_id
) b ON a.site_id = b.site_id AND a.datetime = b.maxDate 

The inner query will get you the MAX(datetime) for each site_id. Then you join it with your table to get the rest of the information.

sqlfiddle demo

Answer 2

SELECT * FROM <tablename> WHERE datetime = <datetime> ORDER BY datetime DESC LIMIT 2

Answer 3

I believe this should work:

SELECT SUBSTRING(`datetime`, 1, 10) AS date, MAX(`views`)
FROM table
GROUP BY SUBSTRING(`datetime`, 1, 10)

If you need the id/site_id as well, write it in your post, as it is not clear

SQLFiddle to show you the result: http://sqlfiddle.com/#!2/e0ccb3/1

Answer 4

You data and examples do not really match themselves, nor the description, but what you probably are looking for is this:

Select top 1 * 
  from table
 where date(datetime) <= date(@PARAMETER)

order by datetime desc