Oracle 23c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
WITH rsqfc (scp, aud, spos, epos) AS (
  SELECT scp,
         aud,
         1,
         INSTR(scp, ' ', 1)
  FROM   JSON_TABLE(
           '{"s": "s1 s2 s3","a": ["a1","a2","a3"]}' FORMAT JSON,
           '$[*]'
           COLUMNS(
             scp VARCHAR2 PATH '$.s',
             NESTED PATH '$.a[*]' COLUMNS(
               aud VARCHAR2 PATH '$[*]'
             )
           )
         )
UNION ALL
  SELECT scp,
         aud,
         epos + 1,
         INSTR(scp, ' ', epos + 1)
  FROM   rsqfc
  WHERE  epos > 0
)
SELECT CASE epos
       WHEN 0
       THEN SUBSTR(scp, spos)
       ELSE SUBSTR(scp, spos, epos - spos)
       END AS scp,
       aud
FROM   rsqfc;


SCP
AUD


s1
a1

s1
a2

s1
a3

s2
a1

s2
a2

s2
a3

s3
a1

s3
a2

s3
a3


SELECT REGEXP_SUBSTR(scp, '[^ ]+', 1, lvl) AS scp,
       aud
FROM   JSON_TABLE(
         '{"s": "s1 s2 s3","a": ["a1","a2","a3"]}' FORMAT JSON,
         '$[*]'
         COLUMNS(
           scp VARCHAR2 PATH '$.s',
           NESTED PATH '$.a[*]' COLUMNS(
             aud VARCHAR2 PATH '$[*]'
           )
         )
       )
       CROSS APPLY (
         SELECT LEVEL AS lvl
         FROM   DUAL
         CONNECT BY LEVEL <= REGEXP_COUNT(scp, '[^ ]+')
       );


SCP
AUD


s1
a1

s2
a1

s3
a1

s1
a2

s2
a2

s3
a2

s1
a3

s2
a3

s3
a3