Obtain values from different tables

Table processes_user
id_user | id_proc
--
35 | 17001
100 | 1089
35 | 17002
Table processes_flow
(example:the process 17001 is with the user 35 and the deadline of the
flow is 2006-07-30! As you can see there are 2 entries on the table
below, the first with a lower id references an old flow, but I want to
get the deadline of the last flow of the process)
--
id | id_proc | deadline
--
10| 17001 | null
12| 1089 | 2006-05-12
15| 17001 | 2006-07-30
20| 17002 | null
--
I would like to get for the user 35 the following info:
17001 | 2006-07-30
17002 | null
How can I do this with a sql command? I would like you to share some
ideas because I'm stuck with this.
Regards,
Hugo SantosSELECT a.id_user, a.id_proc, b.deadline
FROM processes_user a
LEFT JOIN (SELECT id_proc, MAX(deadline) as deadline
FROM processes_flow
GROUP BY id_proc) b ON a.id_proc = b.id_proc
WHERE a.id_user= 35
Untested.
Stu
hugonsan...@.gmail.com wrote:
> Table processes_user
> id_user | id_proc
> --
> 35 | 17001
> 100 | 1089
> 35 | 17002
>
> Table processes_flow
> (example:the process 17001 is with the user 35 and the deadline of the
> flow is 2006-07-30! As you can see there are 2 entries on the table
> below, the first with a lower id references an old flow, but I want to
> get the deadline of the last flow of the process)
> --
> id | id_proc | deadline
> --
> 10| 17001 | null
> 12| 1089 | 2006-05-12
> 15| 17001 | 2006-07-30
> 20| 17002 | null
> --
> I would like to get for the user 35 the following info:
> 17001 | 2006-07-30
> 17002 | null
> How can I do this with a sql command? I would like you to share some
> ideas because I'm stuck with this.
> Regards,
> Hugo Santos|||Stu wrote:
> SELECT a.id_user, a.id_proc, b.deadline
> FROM processes_user a
> LEFT JOIN (SELECT id_proc, MAX(deadline) as deadline
> FROM processes_flow
> GROUP BY id_proc) b ON a.id_proc = b.id_proc
> WHERE a.id_user= 35
>
> Untested.
> Stu
>
Thanks for your reply Stu, but with that aren't you going to get the
max deadline only? I want to show the deadline from the last flow.
For example.. on the first flow you may have a deadline and on the
second the deadline is null. And I want to get the deadline from the
last flow... which is null.
Can you clear this out?|||I'm sorry, I made an assumption that may or may not be true; I'm
assuming that NULL comes before a deadline. In that case, the subquery
will only return rows that have a deadline associated with them; doing
a LEFT JOIN will return the MAX(deadline) if there is one, and NULL if
there is not.
hugos wrote:
> Stu wrote:
> Thanks for your reply Stu, but with that aren't you going to get the
> max deadline only? I want to show the deadline from the last flow.
> For example.. on the first flow you may have a deadline and on the
> second the deadline is null. And I want to get the deadline from the
> last flow... which is null.
> Can you clear this out?|||Thanks.
I already found a different way! I think it's not optimized but it will
work for now ;)
Stu escreveu:
> I'm sorry, I made an assumption that may or may not be true; I'm
> assuming that NULL comes before a deadline. In that case, the subquery
> will only return rows that have a deadline associated with them; doing
> a LEFT JOIN will return the MAX(deadline) if there is one, and NULL if
> there is not.