Как найти верхнюю отметку (для сеансов) в Oracle 9i

Посмотрите, поможет ли это:

WITH X AS
(
    SELECT 
        JSON_ARRAY_ELEMENTS(cod_proj::JSON) AS jsonelement
    FROM temp.kmltests
)
SELECT 
    ROW_NUMBER() OVER (ORDER BY jsonelement->>'A'),
    jsonelement->'A' AS A,

    -- Use a CASE to determine if B is a scalar value or an array.
    -- If B is a scalar value, simply access jsonelement->'B'

    JSON_ARRAY_ELEMENTS(jsonelement->'B')->'C' AS C,
    JSON_ARRAY_ELEMENTS(jsonelement->'B')->'D' AS D
FROM X xx