如何确定SQL中的字符串是否为数字？

SELECT 1 FROM DUAL
WHERE REGEXP_LIKE(\'23.9\', \'^\\d+(\\.\\d+)?$\', \'\') 

SELECT LENGTH(TRIM(TRANSLATE(string1, \' +-.0123456789\', \' \'))) FROM DUAL

FUNCTION is_number(x IN VARCHAR2)
RETURN NUMBER
IS
    PROCEDURE check_number (y IN NUMBER)
    IS
    BEGIN
        NULL;
    END;
BEGIN
    PRAGMA INLINE(check_number, \'No\');
    check_number(TO_NUMBER(x);
    RETURN 1;
EXCEPTION
    WHEN INVALID_NUMBER
    THEN RETURN 0;
END is_number;

var v_test varchar2(20);
EXEC :v_test := \' -24.9 \';

 select
 (case when trim(:v_test) is null then \'N\' ELSE   -- only banks, or null
 (case when instr(trim(:v_test),\'+\',2,1) > 0 then \'N\' ELSE  -- + sign not first char
 (case when instr(trim(:v_test),\'-\',2,1) > 0 then \'N\' ELSE  -- - sign not first char
 (case when instr(trim(:v_test),\' \',1,1) > 0 then \'N\' ELSE  -- internal spaces
 (case when instr(trim(:v_test),\'.\',1,2) > 0 then \'N\' ELSE  -- second decimal point
 (case when LENGTH(TRIM(TRANSLATE(:v_test, \' +-.0123456789\',\' \'))) is not null then \'N\' ELSE  -- only valid numeric charcters.
  \'Y\'
  END)END)END)END)END)END) as is_numeric
  from dual;

LENGTH(TRIM(TRANSLATE(string1, \' +-.0123456789\', \' \'))) is null

LENGTH(TRIM(TRANSLATE(translate(trim(string1),\' \',\'X\'), \'0123456789\', \' \'))) is null

TRIM(TRANSLATE(TRANSLATE(TRIM(\'1 2 3d 4\'), \' \',\'@\'),\'0123456789\',\' \')) is null