Question

I have a table named Logs:

 ->OCCUR_TIME --date and time
 ->NAME --name of a person
 ->KIND --the kind of log (eg. 40 means `something`)
 ->VALUE --the value of the kind of log (eg. 99)

I have to create a query:

SELECT 
*
FROM        LOGS
WHERE       NAME='dude'
ORDER BY    KIND, OCCUR_TIME, VALUE;

Now this displays the logs and sorted by kind, then occur time (if occur_time is exactly the same it will then sort by value).

Notes:

• VALUE of a KIND must always be +1
• If not report a problem.

What if for an example there was a problem with the log and after the VALUE 400 the next VALUE is 398?

Example:

   Occur_Time                | Name    | Kind | Value
   2012-06-26 15:14:25.407     dude      40     398
   2012-06-27 16:55:28.730     dude      40     399
   2012-06-30 02:43:26.763     dude      40     400
   2012-06-30 05:26:32.673     dude      40     398 <-- data prob. (possible rollback)
   2012-06-30 16:35:28.330     dude      40     399 <-- problem continuing
   2012-06-20 20:29:51.207     dude      41     100 <-- no prob. bcoz its another kind
   2012-06-23 05:50:59.130     guy       40     500 <-- no prob. bcoz its another name

I want a query that will find the problem, and where it started. Like this?

Please help. Thank you.

Answer 1

In SQL Server 2012, you would do this using the lag() function.

I’ll assume you are using an earlier version, but post 2005. You can do this with nested windows functions.

select name, KIND, OCCUR_TIME, VALUE,
       (case when max(testval) over (partition by kind, name) <> min(testval) over (partition by kind)
              then 'FAIL'
              else 'OKAY'
        end) as status
from (SELECT *,
             row_number() over (partition by kind, name order by occur_time, value) as seqnum,
             (value - row_number() over (partition by kind, name order by occur_time, value)) as testval
      FROM LOGS
      WHERE NAME='dude'
     ) t
  ORDER BY name, KIND, OCCUR_TIME, VALUE

The idea is to use row_number() to generate a sequence of numbers. The difference between the value and the sequence should be a constant. The outer query looks at the min and max values of these. If they are different, you have a problem.