SQL-forespørgsel til at tælle ændringer af værdier i en kolonne

Fra Oracle 12 kan du bruge MATCH_RECOGNIZE :

SELECT cat,
       month,
       COUNT(*)
FROM   (
  SELECT t.*,
         TRUNC( "DATE", 'MM' ) AS month
  FROM   table_name t
)
MATCH_RECOGNIZE(
  PARTITION BY cat, month
  ORDER BY "DATE", version
  ONE ROW PER MATCH
  AFTER MATCH SKIP TO LAST change_code
  PATTERN ( strt change_code )
  DEFINE
    change_code AS change_code.some_code <> strt.some_code
)
GROUP BY cat, month

Hvilket, for eksempeldata:

CREATE TABLE table_name ( CAT, NR, "DATE", VERSION, SOME_CODE ) AS
SELECT 'ABC',   123,    TIMESTAMP '2009-02-19 00:00:00 UTC',    1,  'OPP' FROM DUAL UNION ALL
SELECT 'ABC',   456,    TIMESTAMP '2009-03-18 00:00:00 UTC',    1,  'ZUM' FROM DUAL UNION ALL
SELECT 'ABC',   444,    TIMESTAMP '2009-03-18 00:00:00 UTC',    1,  'ZUM' FROM DUAL UNION ALL
SELECT 'ABC',   444,    TIMESTAMP '2009-03-18 00:00:00 UTC',    2,  'MUZ' FROM DUAL UNION ALL
SELECT 'ABC',   456,    TIMESTAMP '2009-04-18 00:00:00 UTC',    2,  'XXX' FROM DUAL UNION ALL
SELECT 'ABC',   456,    TIMESTAMP '2009-04-18 00:00:00 UTC',    3,  'XXX' FROM DUAL UNION ALL
SELECT 'ABC',   456,    TIMESTAMP '2009-04-18 00:00:00 UTC',    4,  'UIO' FROM DUAL UNION ALL
SELECT 'ABC',   456,    TIMESTAMP '2009-05-18 00:00:00 UTC',    5,  'RQA' FROM DUAL UNION ALL
SELECT 'DEF',   637,    TIMESTAMP '2018-02-16 00:00:00 UTC',    1,  'FAW' FROM DUAL UNION ALL
SELECT 'DEF',   789,    TIMESTAMP '2018-02-17 00:00:00 UTC',    1,  'WER' FROM DUAL UNION ALL
SELECT 'GHI',   248,    TIMESTAMP '2018-02-17 00:00:00 UTC',    1,  'QWE' FROM DUAL UNION ALL
SELECT 'GHI',   248,    TIMESTAMP '2019-02-17 00:00:00 UTC',    2,  'PPP' FROM DUAL UNION ALL
SELECT 'GHI',   357,    TIMESTAMP '2020-02-16 00:00:00 UTC',    1,  'FFF' FROM DUAL UNION ALL
SELECT 'GHI',   420,    TIMESTAMP '2020-02-16 00:00:00 UTC',    1,  'QDS' FROM DUAL UNION ALL
SELECT 'GHI',   357,    TIMESTAMP '2020-02-16 00:00:00 UTC',    2,  'GGG' FROM DUAL UNION ALL
SELECT 'GHI',   357,    TIMESTAMP '2020-02-16 00:00:00 UTC',    3,  'LLL' FROM DUAL UNION ALL
SELECT 'GHI',   357,    TIMESTAMP '2020-02-16 00:00:00 UTC',    4,  'LLL' FROM DUAL UNION ALL
SELECT 'GHI',   357,    TIMESTAMP '2020-08-16 00:00:00 UTC',    4,  'FFF' FROM DUAL UNION ALL
SELECT 'GHI',   357,    TIMESTAMP '2020-10-16 00:00:00 UTC',    5,  'ZZZ' FROM DUAL

Udgange:

Hvis du vil se ændringerne, kan du bruge:

SELECT *
FROM   (
  SELECT t.*,
         TRUNC( "DATE", 'MM' ) AS month
  FROM   table_name t
)
MATCH_RECOGNIZE(
  PARTITION BY cat, month
  ORDER BY "DATE", version
  MEASURES
    MATCH_NUMBER()     AS mn,
    FIRST( some_code ) AS change_from,
    LAST( some_code )  AS change_to
  ONE ROW PER MATCH
  AFTER MATCH SKIP TO LAST change_code
  PATTERN ( strt change_code )
  DEFINE
    change_code AS change_code.some_code <> strt.some_code
)

Hvilken udgang:

db<>fiddle her

Hvis dit krav til "inden for en måned" er, at du ønsker ændringer, hvor der højst er en måneds forskel mellem den foregående række til den ændrede række, selvom rækkerne er i to forskellige kalendermåneder, (fremfor blot de ændringer, der sker i samme kalendermåned), så kan du bruge:

SELECT cat,
       TRUNC( change_date, 'MM' ) AS month,
       COUNT(*)
FROM   table_name
MATCH_RECOGNIZE(
  PARTITION BY cat
  ORDER BY "DATE", version
  MEASURES
    LAST( "DATE" ) AS change_date
  ONE ROW PER MATCH
  AFTER MATCH SKIP TO LAST change_code
  PATTERN ( strt change_code )
  DEFINE
    change_code AS (
      change_code.some_code <> strt.some_code
      AND MONTHS_BETWEEN( change_code."DATE", strt."DATE" ) <= 1
    )
)
GROUP BY cat, TRUNC( change_date, 'MM' )

Hvilken udgang:

db<>fiddle her