ODPS 不同格式的日期比较大小（取极值）
思路：SQL实现，正则表达式匹配到不同格式然后将其转为同一种格式的日期时间进行比较
例如：将所有的日期格式转换为yyyyddMMhhmmsss的格式
这里是在odps的写的实例，用到正则匹配和正则替换
#取最小值
select distinct tmp1.birthday,tmp1.real_birthday from (select regexp_replace(tmp.birthday, "[-|/|.|\\s|:|年|月|日]", "\\1", 0) as birthday,real_birthday from
(select case when birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|\\.][1-9][-|/|\\.]([1-2]{1}[1-9])|10|20|30|31)$'
then regexp_replace(birthday, '[-|/|\\.|年]', '-0', 1)
when birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|\\.|年](10|11|12)[-|/|\\.|月][1-9])$'
then regexp_replace(birthday, '[-|/|\\.|月]', '-0', 2)
when birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|\\.|年][1-9][-|/|\\.|月][1-9]日{0,1})$'
then regexp_replace(birthday, '[-|/|\\.|年|月]', '-0', 0)
when birthday rlike '^((0[1-9]|(10|11|12))[-|/|\\.](([0-2][1-9])|10|20|30|31)[-|/|\\.]((18|19|([23]\\d))\\d{2,2}))$'
then concat(regexp_replace(birthday, '(0[1-9]|(10|11|12))[-|/|\\.](([0-2][1-9])|10|20|30|31)[-|/|\\.]', '', 0),
regexp_replace(birthday, '[-|/|\\.]((18|19|([23]\\d))\\d{2,2})', '', 0))
else birthday
end as birthday,birthday as real_birthday
from t_status
where birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|年]{0,1}((0{0,1}[1-9])|(10|11|12))[-|/|月]{0,1}(([0-2]{0,1}[1-9])|10|20|30|31)[日]{0,1}\\s*(\\s+(20|21|22|23|[0-1]\\d):{0,1}[0-5]\\d:{0,1}[0-5]\\d(\\.\\d{1,3}){0,1}){0,1})$') tmp
) tmp1 order by tmp1.birthday limit 1;
#取最大值
select tmp1.birthday,tmp1.real_birthday from (select regexp_replace(tmp.birthday, "[-|/|.|\\s|:|年|月|日]", "\\1", 0) as birthday,real_birthday from
(select case when birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|\\.][1-9][-|/|\\.]([1-2]{1}[1-9])|10|20|30|31)$'
then regexp_replace(birthday, '[-|/|\\.|年]', '-0', 1)
when birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|\\.|年](10|11|12)[-|/|\\.|月][1-9])$'
then regexp_replace(birthday, '[-|/|\\.|月]', '-0', 2)
when birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|\\.|年][1-9][-|/|\\.|月][1-9]日{0,1})$'
then regexp_replace(birthday, '[-|/|\\.|年|月]', '-0', 0)
when birthday rlike '^((0[1-9]|(10|11|12))[-|/|\\.](([0-2][1-9])|10|20|30|31)[-|/|\\.]((18|19|([23]\\d))\\d{2,2}))$'
then concat(regexp_replace(birthday, '(0[1-9]|(10|11|12))[-|/|\\.](([0-2][1-9])|10|20|30|31)[-|/|\\.]', '', 0),
regexp_replace(birthday, '[-|/|\\.]((18|19|([23]\\d))\\d{2,2})', '', 0))
else birthday
end as birthday,birthday as real_birthday
from t_status
where birthday rlike '^(((18|19|([23]\\d))\\d{2,2})[-|/|年]{0,1}((0{0,1}[1-9])|(10|11|12))[-|/|月]{0,1}(([0-2]{0,1}[1-9])|10|20|30|31)[日]{0,1}\\s*(\\s+(20|21|22|23|[0-1]\\d):{0,1}[0-5]\\d:{0,1}[0-5]\\d(\\.\\d{1,3}){0,1}){0,1})$') tmp
) tmp1 order by tmp1.birthday desc limit 1;可以处理的日期格式：
2019-06-09
2019-6-9
2019/06/09
2019/6/9
06/09/2019
6/9/2019
06-09-2019
20190609
2019.06.09
2019.6.9
2019年6月9日
2019-06-09 20:00:01
2019/06/09 20:00:01
2019.06.09 20:00:01
06-09-2019 10:50:24
20190609200001
格林威治时间目前木有做匹配；
若同时取最小值和最大值，目前思路是可以使用开窗函数实现，取第一个值和最后一个值；
若有更好的方式实现，请指正指教指导