To_char and to_date Experience Sharing

To_char and to_date Experience Sharing (I) Comparison of the following two methods: to_char (start_time, 'yyyy-mm-dd hh24: mi: ss ') = '2017-06-06 16:18:30 'and start_time = to_date ('2017-06-06 16:18:30', 'yyyy-mm-dd hh24: mi: ss ') the latter is recommended at any time !! (Ii) Simple implementation of converting numbers into English [plain] sys @ ORCL> select to_char (to_date ('20170101', 'J'), 'jj ') as "I love 1314" from dual; I love 1314 ------------------------------------- One Thousand Three Hundred Fourteen (3) A to_date trap. We can use the to_date function to construct any time that we want, in MI and SS, oracle is set to 0 by default, that is, when DD is omitted from the whole day, oracle is set to 1 by default, that is: when MM is omitted, Will oracle be rounded to the year? We will all think in inertia: Yes. Of course, neither! Oracle will not get the whole year, and it will get the whole year to the current month!