Oracle 21c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE table_name (Key, rule, version, RuleAvailable) AS
SELECT 'Class1', 'Csx',        '02.01', 'Yes' FROM DUAL UNION ALL
SELECT 'Class1', 'Csx',        '01.01', 'Yes' FROM DUAL UNION ALL
SELECT 'Class1', 'CsxBusrule', '02.01', 'Withdrawn' FROM DUAL UNION ALL
SELECT 'Class1', 'CsxBusrule', '01.01', 'Yes' FROM DUAL UNION ALL
SELECT 'Class1', 'Csxfw',      '01.01', 'Yes' FROM DUAL UNION ALL
SELECT 'Class2', 'Csx',        '02.01', 'Yes' FROM DUAL UNION ALL
SELECT 'Class2', 'CsxBusrule', '02.01', 'Yes' FROM DUAL UNION ALL
SELECT 'Class3', 'Csxfw',      '01.01', 'Yes' FROM DUAL
8 rows affected

ALTER TABLE table_name ADD class VARCHAR2(50) GENERATED ALWAYS AS (
  key || '-' || rule || '-' || version
)
SELECT Key,
       Class, 
       Rule, 
       Version,
       RuleAvailable
FROM   (
         SELECT Key,
                Class, 
                Rule, 
                Version,
                RuleAvailable,
                DECODE(rule, 'CsxBusrule', 1, 'Csx', 2, 'Csxfw', 3) AS rule_priority,
                DECODE(ruleavailable, 'Withdrawn', 1, 'Yes', 2) AS available_priority
         FROM   table_name
       )
       MATCH_RECOGNIZE(
         PARTITION BY key
         ORDER BY rule_priority, available_priority, version DESC
         ALL ROWS PER MATCH
         PATTERN (^ {- ( withdrawn+ same_rule* )* -} not_withdrawn )
         DEFINE
           withdrawn AS RuleAvailable = 'Withdrawn',
           same_rule AS Rule = PREV(rule)
       )


KEY
CLASS
RULE
VERSION
RULEAVAILABLE


Class1
Class1-Csx-02.01
Csx
02.01
Yes

Class2
Class2-CsxBusrule-02.01
CsxBusrule
02.01
Yes

Class3
Class3-Csxfw-01.01
Csxfw
01.01
Yes


SELECT Key,
       Class, 
       Rule, 
       Version,
       RuleAvailable
FROM   (
  SELECT Key,
         Class, 
         Rule, 
         Version,
         RuleAvailable,
         ROW_NUMBER() OVER (
           PARTITION BY key
           ORDER BY rule_priority, version DESC
         ) AS rn
  FROM   (
    SELECT Key,
           Class, 
           Rule, 
           Version,
           RuleAvailable,
           COUNT(CASE RuleAvailable WHEN 'Withdrawn' THEN 1 END) OVER (
             PARTITION BY key, rule
           ) AS num_withdrawn,
           DECODE(rule, 'CsxBusrule', 1, 'Csx', 2, 'Csxfw', 3) AS rule_priority
    FROM   table_name
  )
  WHERE  num_withdrawn = 0
)
WHERE  rn = 1;


KEY
CLASS
RULE
VERSION
RULEAVAILABLE


Class1
Class1-Csx-02.01
Csx
02.01
Yes

Class2
Class2-CsxBusrule-02.01
CsxBusrule
02.01
Yes

Class3
Class3-Csxfw-01.01
Csxfw
01.01
Yes
KEY	CLASS	RULE	VERSION	RULEAVAILABLE
Class1	Class1-Csx-02.01	Csx	02.01	Yes
Class2	Class2-CsxBusrule-02.01	CsxBusrule	02.01	Yes
Class3	Class3-Csxfw-01.01	Csxfw	01.01	Yes