Question

Oracle comparing dates

Asked by: Peewee

Hi There,
as an example I have timestamp columns in my table: t1, t2, t3 & t4 and 4 varchar columns in my table v1, v2, v3 & v4. I need to compare all four timestamp columns in work out which is the most recent. if t1 is the most recent then i want to select t1 & v1 as time and value. if t2 is the most recent i want to select t2 & v2 as time and value, if t3 is the most recent i want to select t3 & v3 as time and value and so on.

I was thinking to use a decode or case statement though i'm not sure how to perform the comparisons?
Can you help me write some sample sql which will fulfill this requirement.

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Asked On
2008-01-22 at 10:56:18ID23102117
Tags

dates

,

oracle

,

comparing

Topic

Oracle Database

Participating Experts
2
Points
50
Comments
6

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Answers

 

by: sdstuberPosted on 2008-01-22 at 10:59:25ID: 20717088

decode(least(t1,t2,t3,t4),t1,v1,t2,v2,t3,v3,t4,v4)

 

by: sdstuberPosted on 2008-01-22 at 11:00:23ID: 20717108

actually, use GREATEST, not LEAST,  since you wanted most recent.  sorry, first post was for oldest

decode(greatest(t1,t2,t3,t4),t1,v1,t2,v2,t3,v3,t4,v4)

 

by: markgeerPosted on 2008-01-22 at 12:59:07ID: 20718250

The full statement then would be something like this:
select greatest(t1,t2,t3,t4) "Time",  decode(greatest(t1,t2,t3,t4),t1,v1,t2,v2,t3,v3,t4,v4) "Value"
from {your_table]
where...

Note that (depending on which application you use for this) you may need to set your NLS_DATE_FORMAT manually if you want to see the actual time-of-day for the timestamp.

Also, it looks like your table structure is not ideal for answering this question with the data in an Oracle table.  Whenever you use table structures in Oracle that do not contain normalized data, the queries and updates become much more complex.

 

by: PeeweePosted on 2008-01-23 at 08:57:27ID: 20725024

many thx for the repsonses.. i will review them..

 

by: PeeweePosted on 2008-01-30 at 11:29:13ID: 20780239

after looking and playing with the code i have noticed that is one of the values is blank/null, then it displays the null and not the most recent timestamp. How should i ammend the code?

ie. in my example below  fcm_tsp_prv_app_mk is null as a consequence last update time is null.
   greatest( fcm_tsp_cur_app_mk, fpp_tsp_cur_trd_mk, fcm_tsp_prv_app_mk,  fpp_tsp_prv_trd_mk) as last_update_time,

 

by: sdstuberPosted on 2008-01-30 at 13:11:33ID: 20781366

wrap each nullable value in an NVL that sets to some long ago default date.
Like January 1, 1900  (go back earlier if necessary)

greatest(
    NVL(fcm_tsp_cur_app_mk,  TO_DATE('19000101','yyyymmdd')),
    NVL(fcm_tsp_cur_trd_mk,  TO_DATE('19000101','yyyymmdd')),
    NVL(fcm_tsp_prv_app_mk,  TO_DATE('19000101','yyyymmdd')),
    NVL(fpp_tsp_prv_trd_mk, TO_DATE('19000101','yyyymmdd'))
)

20120131-EE-VQP-002

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