postgresql时间函数

验证了一波postgresql中between对于时间的开闭情况
大概的结论是左闭右开 [ )，但也有例外

select '2017-12-31 24:00:00' = '2018-01-01 00:00:00'  False
select '2017-12-31 24:00:00' < '2018-01-01 00:00:00'  True

select '2017-01-01' between '2017-01-01' and '2018-01-01'   True
select '2018-01-01' between '2017-01-01' and '2018-01-01'   True

select '2017-12-31 24:00:00' between '2017-01-01' and '2018-01-01'   True
select '2018-01-01 00:00:00' between '2017-01-01' and '2018-01-01'   False

select '2018-01-01 00:00:00' between '2017-01-01 00:00:00' and '2018-01-01 00:00:00'  True

根据两个日期，生成之间的日期
select to_date(to_char(generate_series('2014-01-01'::date,'2014-02-02', '1 days'),'yyyy-mm-dd'),'yyyy-mm-dd')::date

两个日期之间的天数（包括两头的日期，所以+1）
select extract(day from(age(to_date('2014-01-02','yyyy-mm-dd'),to_date('2014-01-01','yyyy-mm-dd'))))+1