Finding a 'run' of rows from an ordered result set - sql

Question

I'm trying to figure out a way of identifying a "run" of results (successive rows, in order) that meet some condition. Currently, I'm ordering a result set, and scanning by eye for particular patterns. Here's an example:
SELECT the_date, name
FROM orders
WHERE
the_date BETWEEN
to_date('2013-09-18',..) AND
to_date('2013-09-22', ..)
ORDER BY the_date
--------------------------------------
the_date | name
--------------------------------------
2013-09-18 00:00:01 | John
--------------------------------------
2013-09-19 00:00:01 | James
--------------------------------------
2013-09-20 00:00:01 | John
--------------------------------------
2013-09-20 00:00:02 | John
--------------------------------------
2013-09-20 00:00:03 | John
--------------------------------------
2013-09-20 00:00:04 | John
--------------------------------------
2013-09-21 16:00:01 | Jennifer
--------------------------------------
What I want to extract from this result set is all the rows attributed to John on 2013-09-20. Generally what I'm looking for is a run of results from the same name, in a row, >= 3. I'm using Oracle 11, but I'm interested to know if this can be achieved with strict SQL, or if some kind of analytical function must be used.

Answer 1

You need multiple nested window functions:
SELECT *
FROM
(
SELECT the_date, name, grp,
COUNT(*) OVER (PARTITION BY grp) AS cnt
FROM
(
SELECT the_date, name,
SUM(flag) OVER (ORDER BY the_date) AS grp
FROM
(
SELECT the_date, name,
CASE WHEN LAG(name) OVER (ORDER BY the_date) = name THEN 0 ELSE 1 END AS flag
FROM orders
WHERE
the_date BETWEEN
TO_DATE('2013-09-18',..) AND
TO_DATE('2013-09-22', ..)
) dt
) dt
) dt
WHERE cnt >= 3
ORDER BY the_date

Answer 2

Try this
WITH ORDERS
AS (SELECT
TO_DATE ( '2013-09-18 00:00:01',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'John' AS NAME
FROM
DUAL
UNION ALL
SELECT
TO_DATE ( '2013-09-19 00:00:01',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'James' AS NAME
FROM
DUAL
UNION ALL
SELECT
TO_DATE ( '2013-09-20 00:00:01',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'John' AS NAME
FROM
DUAL
UNION ALL
SELECT
TO_DATE ( '2013-09-20 00:00:02',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'John' AS NAME
FROM
DUAL
UNION ALL
SELECT
TO_DATE ( '2013-09-20 00:00:03',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'John' AS NAME
FROM
DUAL
UNION ALL
SELECT
TO_DATE ( '2013-09-20 00:00:04',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'John' AS NAME
FROM
DUAL
UNION ALL
SELECT
TO_DATE ( '2013-09-21 16:00:01',
'YYYY-MM-DD HH24:MI:SS' )
AS THE_DATE,
'Jennifer' AS NAME
FROM
DUAL)
SELECT
B.*
FROM
(SELECT
TRUNC ( THE_DATE ) THE_DATE,
NAME,
COUNT ( * )
FROM
ORDERS
WHERE
THE_DATE BETWEEN TRUNC ( TO_DATE ( '2013-09-18',
'YYYY-MM-DD' ) )
AND TRUNC ( TO_DATE ( '2013-09-22',
'YYYY-MM-DD' ) )
GROUP BY
TRUNC ( THE_DATE ),
NAME
HAVING
COUNT ( * ) >= 3) A,
ORDERS B
WHERE
A.NAME = B.NAME
AND TRUNC ( A.THE_DATE ) = TRUNC ( B.THE_DATE );
OUTPUT
9/20/2013 12:00:01 AM John
9/20/2013 12:00:02 AM John
9/20/2013 12:00:03 AM John
9/20/2013 12:00:04 AM John