HANA SQL IsDate（）等价或获取无效数据的to_date函数？

Question

select ISDATE('20170213') from dummy;

select ISDATE('JUNK') from dummy;

如何操作是HANA SQL。

Answer 1

好，这似乎行得通。

select DATS_IS_VALID('20170213') from dummy; -- 1 -- expects YYYYMMDD only

select DATS_IS_VALID('2017-0213') from dummy; -- 0
select DATS_IS_VALID('2017-02-13') from dummy; -- 0
select DATS_IS_VALID('20170233') from dummy; -- 0
select DATS_IS_VALID('21-02-2017') from dummy; -- 0
select DATS_IS_VALID('02212017') from dummy; -- 0

另请参见tstmp_is_valid（）了解时间戳。另请参阅here

或者，使用UDF-仅采用YYYYMMDD和YYYY-MM-DD

--DROP FUNCTION ISDATE;
CREATE FUNCTION ISDATE (inputval NVARCHAR(100))

-- expects format YYYYMMDD
RETURNS RETURNVAL BOOLEAN
LANGUAGE SQLSCRIPT
AS
BEGIN
DECLARE DT date;

   DECLARE EXIT HANDLER FOR SQLEXCEPTION

        BEGIN

   RETURNVAL := false;

        END;

   select CAST(:inputval AS DATE) into DT from dummy;
    RETURNVAL := true;


END;
select ISDATE('20170213') from dummy; --true
select ISDATE('2017-02-13') from dummy; --true
select ISDATE('2017-FEB-13') from dummy; --false
select ISDATE('13-12-2017') from dummy; --false
select ISDATE('abc') from dummy; --false
select ISDATE('13-Dec-2017') from dummy; --false
select ISDATE('20170232') from dummy; --false

这里是处理错误数据的“截止日期”，如果无效，则返回NULL，请确保您所有的日期都与格式字符串匹配，否则它将转换为null。

CREATE FUNCTION TO_DATE_V2 (inputval NVARCHAR(100), format_str NVARCHAR(20))


RETURNS RETURNVAL DATE
LANGUAGE SQLSCRIPT
AS
BEGIN
DECLARE DT date;

   DECLARE EXIT HANDLER FOR SQLEXCEPTION

        BEGIN

   RETURNVAL := NULL;

        END;

   select TO_DATE(:inputval, :format_str) into DT from dummy;
    RETURNVAL := :DT;

END;

select TO_DATE_V2('20-04/2017', 'DD/MM/YYYY') from dummy;  -- null
select TO_DATE_V2('20/04/2017', 'DD/MM/YYYY') from dummy;  -- 2017-04-20
select TO_DATE_V2('JUNK', 'DD/MM/YYYY') from dummy;  -- null