Zkontrolujte formát DATE v Oracle

Vytvořte uživatelem definovanou funkci a pokuste se analyzovat datum; pokud existují nějaké výjimky, zachyťte je a vraťte svůj výchozí řetězec.

CREATE FUNCTION check_Date (
  datestring    VARCHAR2,
  format_mask   VARCHAR2 := 'FXMMDDYYYY',
  default_value VARCHAR2 := '00000000'
) RETURN VARCHAR2 DETERMINISTIC
IS
  INVALID_DATE EXCEPTION;
  PRAGMA EXCEPTION_INIT( INVALID_DATE, -20001 );

  p_date DATE;
BEGIN
  IF datestring IS NULL THEN
    RAISE INVALID_DATE;
  END IF;

  p_date := TO_DATE( datestring, format_mask );

  RETURN datestring;
EXCEPTION
  WHEN OTHERS THEN
    RETURN default_value;
END check_Date;
/

Alternativa :

SELECT CASE
       WHEN NOT REGEXP_LIKE( datestring, '^(0[1-9]|1[12])(0[1-9]|[12]\d|3[01])\d{4}$' )
       THEN '00000000'
       WHEN TO_CHAR(
              ADD_MONTHS(
                TRUNC( TO_DATE( SUBSTR( datestring, 5 ), 'YYYY' ), 'YYYY' ),
                TO_NUMBER( SUBSTR( datestring, 1, 2 ) ) - 1
              )
              + TO_NUMBER( SUBSTR( datestring, 3, 2 ) ) - 1,
              'MMDDYYYY'
            )
            <> datestring
       THEN '00000000'
       ELSE datestring
       END
FROM   your_table