Count only when the next row is different from the previous row - sql

Question

I have a table with 12 registers. I want to count the row just if the column "AREA_OPERATIVA" is different from the previous row (ordering by date asc).
For example, from row 1 to row 2 it shouldn't count anything because both have same area 'CROSS' but between rows 2 and 3, it should count (or sum 1, I don't care) since 'CROSS' and 'UTRDANIOS' are different. So the final count should be 3 for the whole table.
Is it possible to do this via query or do I need to make a script with a cursor for this purpose?
I've tried this:
SELECT a.creclama,
sum (CASE WHEN b.area_operativa NOT LIKE a.area_operativa THEN 1 ELSE 0 END) AS increment
FROM TR_ASGAREOPE a
INNER JOIN TR_ASGAREOPE b ON a.creclama = b.creclama
and a.cdistribuidora = b.cdistribuidora
and a.secuencia = b.secuencia
WHERE a.creclama = 10008354
group by a.creclama;
But is counting the full 12 rows.
EDIT:
Finally I could resolve this by the next query:
select sum (
CASE WHEN (comparacion.area_operativa not like comparacion.siguiente_fila THEN 1 ELSE 0 END) AS incremento
from (
select creclama,
area_operativa,
lead(area_operativa) over (order by fmodifica) as siguiente_fila
from TR_ASGAREOPE
where creclama = 10008354
order by fmodifica
);
Hope it is useful for someone in the future, it really got me stuck for a day. Thank you all guys.

Answer 1

You could try using analytic functions like lead or lag, for example
SELECT CRECLAMA,
CASE WHEN AREA_OPERATIVA <> NEXTROW THEN 1 ELSE 0 END AS INCREMENT
FROM (
SELECT CRECLAMA,
AREA_OPERATIVA,
LEAD(AREA_OPERATIVA) OVER (PARTITION BY 1 ORDER BY CRECLAMA) AS NEXTROW
FROM TR_ASGAREOPE
)

Answer 2

Here's an approach using LEAD:
WITH TR_ASGAREOPE(CRECLAMA, AREA_OPERATIVA, DATE_FIELD) AS
(SELECT 10008354, 'CROSS', DATE '2019-01-01' FROM DUAL UNION ALL
SELECT 10008354, 'CROSS', DATE '2019-01-02' FROM DUAL UNION ALL -- 1
SELECT 10008354, 'UTRDANIOS', DATE '2019-01-03' FROM DUAL UNION ALL -- 2
SELECT 10008354, 'EXP263', DATE '2019-01-04' FROM DUAL UNION ALL -- 3
SELECT 10008354, 'EXP6', DATE '2019-01-05' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-06' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-07' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-08' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-09' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-10' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-11' FROM DUAL UNION ALL
SELECT 10008354, 'EXP6', DATE '2019-01-12' FROM DUAL UNION ALL
SELECT 12345678, 'AREA49', DATE '2019-02-01' FROM DUAL UNION ALL
SELECT 12345678, 'AREA49', DATE '2019-02-02' FROM DUAL UNION ALL -- 1
SELECT 12345678, 'AREA50', DATE '2019-02-03' FROM DUAL UNION ALL
SELECT 12345678, 'AREA50', DATE '2019-02-04' FROM DUAL UNION ALL -- 2
SELECT 12345678, 'AREA52', DATE '2019-02-05' FROM DUAL UNION ALL
SELECT 12345678, 'AREA52', DATE '2019-02-06' FROM DUAL UNION ALL
SELECT 12345678, 'AREA52', DATE '2019-02-07' FROM DUAL UNION ALL -- 3
SELECT 12345678, 'AREA53', DATE '2019-02-08' FROM DUAL UNION ALL -- 4
SELECT 12345678, 'AREA52', DATE '2019-02-09' FROM DUAL UNION ALL -- 5
SELECT 12345678, 'AREA53', DATE '2019-02-10' FROM DUAL),
cteData AS (SELECT CRECLAMA,
LEAD(CRECLAMA) OVER (ORDER BY DATE_FIELD) AS NEXT_CRECLAMA,
AREA_OPERATIVA,
LEAD(AREA_OPERATIVA) OVER (ORDER BY DATE_FIELD) AS NEXT_AREA_OPERATIVA
FROM TR_ASGAREOPE)
SELECT CRECLAMA, COUNT(*)
FROM cteData
WHERE CRECLAMA = NEXT_CRECLAMA AND
AREA_OPERATIVA <> NEXT_AREA_OPERATIVA
GROUP BY CRECLAMA
ORDER BY CRECLAMA;
I added data for another CRECLAMA value to show how it would work.
Results:
CRECLAMA COUNT(*)
10008354 3
12345678 5
dbfiddle here

Answer 3

You can use lag() analytic function :
with t as
(
select a.*,
lag(a.area_operativa,1,a.area_operativa) over (order by a."date") as lg
from asgareope a
where a.creclama = 10008354
)
select t.creclama, sum(case when lg = area_operativa then 0 else 1 end) as "increment"
from t
group by t.creclama

Answer 4

I think you can simple use COUNT(DISTINCT ...) for your problem, if the AREA_OPERATIVA could not return to previously used value:
SELECT CRECLAMA, COUNT(DISTINCT AREA_OPERATIVA)
FROM TR_ASGAREOPE
GROUP BY CRECLAMA