WITH recursive R0 AS (
  SELECT CAST('F1 Name,F2 SEX,F3 Age,' AS VARCHAR(1000)) AS InStr FROM RDB$DATABASE
), R1 AS (
  SELECT substring(InStr FROM 1 FOR position(' ' IN InStr) - 1) AS Field,
    substring(InStr FROM position(' ' IN InStr) + 1 FOR position(',' IN InStr) - 1 - position(' ' IN InStr)) AS FieldName,
    substring(InStr FROM position(',' IN InStr) + 1) AS InStr
  FROM R0

  UNION ALL

  SELECT substring(InStr FROM 1 FOR position(' ' IN InStr) - 1) AS Field,
    substring(InStr FROM position(' ' IN InStr) + 1 FOR position(',' IN InStr) - 1 - position(' ' IN InStr)) AS FieldName,
    substring(InStr FROM position(',' IN InStr) + 1) AS InStr
  FROM R1
  WHERE position(',' IN InStr) > 0
)
SELECT Field, FieldName FROM R1