UNDEFINE TEXT
WITH STRING AS
(SELECT '&&TEXT' STR
FROM DUAL),
ARRAY_STRING AS
(SELECT STR, SUBSTR(STR, LEVEL, 1) SS, ROWNUM RN
FROM STRING
CONNECT BY LEVEL <= LENGTH(STR)),
PARENTHESIS AS
(SELECT STR, SS, RN
FROM ARRAY_STRING
WHERE SS IN ('(',')')
ORDER BY RN),
DE_PARENTHESIS AS
(SELECT STR,
        CASE
            WHEN SS = '(' THEN 1
            WHEN SS = ')' THEN -1
            ELSE 0
        END SS
FROM ARRAY_STRING),
CHECK_PARENTHESIS AS
(SELECT STR, CASE
            WHEN SUM(SS) <> 0 THEN 0
            ELSE 1
        END CHECK_P
FROM DE_PARENTHESIS
GROUP BY STR)
SELECT
    CASE
        WHEN CHECK_P <> 0 THEN STR
    ELSE ''
    END
FROM CHECK_PARENTHESIS;