Обсуждение: maximum count of contiguous years

is there a way to get the maximum count of contiguous years? for example:

SELECT version();
PostgreSQL 8.3.1, compiled by Visual C++ 1400

CREATE TABLE sch_applform
(
  scholar_id integer NOT NULL,
  award_year numeric(4) NOT NULL,
  CONSTRAINT sch_applform_pkey PRIMARY KEY (scholar_id, award_year)
)
WITH (OIDS=FALSE);

INSERT INTO sch_applform VALUES (1, 1994);
INSERT INTO sch_applform VALUES (1, 1995);
INSERT INTO sch_applform VALUES (1, 1996);
INSERT INTO sch_applform VALUES (1, 1997);
INSERT INTO sch_applform VALUES (1, 1999);
INSERT INTO sch_applform VALUES (1, 2000);
INSERT INTO sch_applform VALUES (1, 2001);

INSERT INTO sch_applform VALUES (2, 1994);
INSERT INTO sch_applform VALUES (2, 1996);
INSERT INTO sch_applform VALUES (2, 1997);
INSERT INTO sch_applform VALUES (2, 1998);
INSERT INTO sch_applform VALUES (2, 1999);
INSERT INTO sch_applform VALUES (2, 2000);
INSERT INTO sch_applform VALUES (2, 2002);

INSERT INTO sch_applform VALUES (3, 1994);
INSERT INTO sch_applform VALUES (3, 1995);
INSERT INTO sch_applform VALUES (3, 1997);
INSERT INTO sch_applform VALUES (3, 1998);
INSERT INTO sch_applform VALUES (3, 2000);
INSERT INTO sch_applform VALUES (3, 2001);

is there a select statement containing 'AND award_year BETWEEN 1994
AND 2002' that could generate the following?
scholar_id    consistent_yrs
         1                 4
         2                 5
         3                 2

thanks in advance

gorsa <gorsa.1972@gmail.com> wrote:

> [...]
> is there a select statement containing 'AND award_year BETWEEN 1994
> AND 2002' that could generate the following?
> scholar_id    consistent_yrs
>          1                 4
>          2                 5
>          3                 2

You could either do some wild fancy query where you parti-
tion the data by scholar_id, then by award_year, then filter
on the condition that the sum of award_year and RANK() (?)
less one equals the current award_year, find the maximum of
those, ...

  ... or you could just write a short function in your ap-
plication (or a set-returning PL/pgSQL function if your ap-
plication is dumb).

Tim

thanks tim. will read up on rank() and pl/pgsql.