日付 YYYYMMDD が妥当な内容か? Oracle PL/SQL #SQL

IS_YYYYMMDD

CREATE OR REPLACE FUNCTION IS_YYYYMMDD
    (
    IN_YYYYMMDD IN VARCHAR2 -- YYYYMMDD
    )
    RETURN VARCHAR2 -- 'OK' or 'NG'
--
--  日付 YYYYMMDD が妥当な内容か判断する。
--
IS
    L_DATE DATE ;
BEGIN
    L_DATE := TO_DATE(IN_YYYYMMDD, 'YYYYMMDD') ;
    RETURN('OK') ;
EXCEPTION
    WHEN OTHERS THEN
        RETURN('NG') ; -- エラー
END IS_YYYYMMDD ;
/
-- ↓実行権をPUBLICにし、インスタンスの全スキーマから実行可能に
-- https://docs.oracle.com/cd/E57425_01/121/SQLRF/statements_9014.htm#i2155015  SQL language reference
GRANT EXECUTE ON IS_YYYYMMDD TO PUBLIC ;
-- ↓PUBLIC SYNONYM に
-- http://docs.oracle.com/cd/E57425_01/121/SQLRF/statements_7001.htm#CJAJCDDF  SQL language reference
CREATE OR REPLACE PUBLIC SYNONYM IS_YYYYMMDD FOR IS_YYYYMMDD ;

-- 使用例
SQL> COLUMN YYYYMMDD    FORMAT A10
SQL> COLUMN IS_YYYYMMDD FORMAT A10
SQL> WITH DATE_LIST AS  -- since Oracle11.1.0
  2      (
  3      SELECT '20160229' AS YYYYMMDD FROM DUAL UNION ALL
  4      SELECT '20170229'             FROM DUAL UNION ALL
  5      SELECT '20180229'             FROM DUAL UNION ALL
  6      SELECT '20190229'             FROM DUAL UNION ALL
  7      SELECT '20200229'             FROM DUAL UNION ALL
  8      SELECT '20210229'             FROM DUAL
  9     )
 10  SELECT DL.YYYYMMDD
 11       , IS_YYYYMMDD(DL.YYYYMMDD) AS IS_YYYYMMDD
 12  FROM DATE_LIST DL ;

YYYYMMDD   IS_YYYYMMD
---------- ----------
20160229   OK
20170229   NG
20180229   NG
20190229   NG
20200229   OK
20210229   NG

6行が選択されました。