Analytic type functionality, matching patters in a column then increment an integer
I can do this in excel with vba, though due to the volume of data that is
now impracticable and I am trying to move most of my logic into the query
and db for analysis.
Looking at the analytic functions I see no way to carry values over the way
they need to be.
Example column:
I have a column that evaluates to either tf,tt,ft,ff (true false matches).
tf means the start of a section,
tt mans intermediary but in the good section
ft means the end of the section that needs to be marked.
ff is just ignored
so I can have
'evaluation'
tf
tt
ft
ff
ff
tf
ft
and would like to have a column indicate like this:
'evaluation' 'indicator'
tf 1
tt 1
ft 1
ff
ff
tf 2
ft 2
tf 3
tt 3
ft 3
ff
I have tried rank() and some case statements though I can quite seem to get
the sql to be aware across rows as shown in the desired indicator column
noted above.
It seems like I am missing something that would we aware like that. Any
ideas? Thanks in advance.
On 05/10/11 19:29, Henry Drexler wrote:
and would like to have a column indicate like this:
'evaluation' 'indicator'
tf 1
tt 1
ft 1
ff
ff
tf 2
ft 2
tf 3
tt 3
ft 3
ff
SELECT id,evaluation,sum(case when evaluation='tf' then 1 else 0 end)
over (order by id) FROM tfcount ORDER BY id;
id | evaluation | sum
----+------------+-----
1 | tf | 1
2 | tt | 1
3 | ft | 1
4 | ff | 1
5 | ff | 1
6 | tf | 2
7 | ft | 2
8 | tf | 3
9 | tt | 3
10 | ft | 3
11 | ff | 3
(11 rows)
OK, so that's almost it, but you'd like "ff" to be null. You probably
can do it with a suitably nested CASE, but it's probably clearer as a
sub-query.
SELECT
id,
evaluation,
CASE WHEN evaluation='ff' THEN null::int
ELSE sum::int END AS section_num
FROM (
SELECT
id,
evaluation,
sum(case when evaluation='tf' then 1 else 0 end) over (order by id)
FROM tfcount
) AS rows
ORDER BY id;
HTH
P.S. - I always find the windowing function syntax confusing, but it's
as the standards define I believe.
--
Richard Huxton
Archonet Ltd
that was spot on Richard. Thank you for your time and the solution.
On Wed, Oct 5, 2011 at 3:22 PM, Richard Huxton <dev@archonet.com> wrote:
Show quoted text
On 05/10/11 19:29, Henry Drexler wrote:
and would like to have a column indicate like this:
'evaluation' 'indicator'
tf 1
tt 1
ft 1
ff
ff
tf 2
ft 2
tf 3
tt 3
ft 3
ffSELECT id,evaluation,sum(case when evaluation='tf' then 1 else 0 end) over
(order by id) FROM tfcount ORDER BY id;id | evaluation | sum
----+------------+-----
1 | tf | 1
2 | tt | 1
3 | ft | 1
4 | ff | 1
5 | ff | 1
6 | tf | 2
7 | ft | 2
8 | tf | 3
9 | tt | 3
10 | ft | 3
11 | ff | 3
(11 rows)OK, so that's almost it, but you'd like "ff" to be null. You probably can
do it with a suitably nested CASE, but it's probably clearer as a sub-query.SELECT
id,
evaluation,
CASE WHEN evaluation='ff' THEN null::int
ELSE sum::int END AS section_num
FROM (
SELECT
id,
evaluation,
sum(case when evaluation='tf' then 1 else 0 end) over (order by id)
FROM tfcount
) AS rows
ORDER BY id;HTH
P.S. - I always find the windowing function syntax confusing, but it's as
the standards define I believe.--
Richard Huxton
Archonet Ltd