oracle 把时间戳字符串，转换成日期格式

create or replace function func_from_timestamp_str_to_date_str(
                       in_timestamp_str   in varchar2
)
return varchar2 as
    v_result  varchar2(100);
    v_str varchar2(100);
    v_number number;
begin
    v_str := substr(in_timestamp_str,0,10);
    v_number := to_number(v_str);
    v_result := to_char( TIMESTAMP '1970-01-01 08:00:00' + NUMTODSINTERVAL(v_number, 'SECOND') , 'yyyy-mm-dd hh24:mi:ss' );
    return v_result;

--exception
--  when others then
--    return('');
end;