can this problem be solved with a single SQL query?
- by PierrOz
I have the two following tables (with some sample datas)
LOGS:
ID | SETID | DATE
========================
1 | 1 | 2010-02-25
2 | 2 | 2010-02-25
3 | 1 | 2010-02-26
4 | 2 | 2010-02-26
5 | 1 | 2010-02-27
6 | 2 | 2010-02-27
7 | 1 | 2010-02-28
8 | 2 | 2010-02-28
9 | 1 | 2010-03-01
STATS:
ID | OBJECTID | FREQUENCY | STARTID | ENDID
=============================================
1 | 1 | 0.5 | 1 | 5
2 | 2 | 0.6 | 1 | 5
3 | 3 | 0.02 | 1 | 5
4 | 4 | 0.6 | 2 | 6
5 | 5 | 0.6 | 2 | 6
6 | 6 | 0.4 | 2 | 6
7 | 1 | 0.35 | 3 | 7
8 | 2 | 0.6 | 3 | 7
9 | 3 | 0.03 | 3 | 7
10 | 4 | 0.6 | 4 | 8
11 | 5 | 0.6 | 4 | 8
7 | 1 | 0.45 | 5 | 9
8 | 2 | 0.6 | 5 | 9
9 | 3 | 0.02 | 5 | 9
Every day new logs are analyzed on different sets of objects and stored in table LOGS.
Among other processes, some statistics are computed on the objects contained into these sets and the result are stored in table STATS. These statistic are computed through several logs (identified by the STARTID and ENDID columns).
So, what could be the SQL query that would give me the latest computed stats for all the objects with the corresponding log dates.
In the given example, the result rows would be:
OBJECTID | SETID | FREQUENCY | STARTDATE | ENDDATE
======================================================
1 | 1 | 0.45 | 2010-02-27 | 2010-03-01
2 | 1 | 0.6 | 2010-02-27 | 2010-03-01
3 | 1 | 0.02 | 2010-02-27 | 2010-03-01
4 | 2 | 0.6 | 2010-02-26 | 2010-02-28
5 | 2 | 0.6 | 2010-02-26 | 2010-02-28
So, the most recent stats for set 1 are computed with logs from feb 27 to march 1 whereas stats for set 2 are computed from feb 26 to feb 28.
object 6 is not in the results rows as there is no stat on it within the last period of time.
Last thing, I use MySQL.
Any Idea ?
