首先，来介绍一下Oracle的overlaps函数的用法：
overlaps函数是用来判断两个时间段是否有重叠的
比如说计算 (a,b),(c,d)
就可以写成：
select * from dual where (a,b) overlaps (c,d);
其中abcd都是日期格式。
注意：比较的只能是日期。如果是数字，则会报错 ORA-00932: inconsistent datatypes
最近项目在使用db2数据库，遇到overlaps函数需要转换成db2中的语法方言，其实就是转换为通用的sql语法。
对应的写法有：
判断两个时间段是否有重叠
(a,b),(c,d)
判断两段时间是否有重叠
方法一
select ‘yes‘ from dual where d>a and c<b;
例子：
select *
from PMK_PLANNING_INFO
where id = ‘U2KsqII5NdumrClO5td‘
and to_date(‘2019/07/27‘, ‘YYYY/MM/DD‘) > to_date(begin_time)
and to_date(‘2018/06/27‘, ‘YYYY/MM/DD‘) < to_date(end_time);
方法二
select ‘yes‘ from dual where (a, b) overlaps (c,d);
例子：
select *
from PLANNING_INFO
where id = ‘001‘
and (to_date(begin_time), to_date(end_time))
overlaps
(to_date(‘2018/06/27‘, ‘YYYY/MM/DD‘),
to_date(‘2019/07/27‘, ‘YYYY/MM/DD‘));
方法三
select ‘yes‘ from dual where a between c and d or d between a and b;
例子：
select *
from PMK_PLANNING_INFO
where id = ‘U2KsqII5NdumrClO5td‘
and to_date(begin_time) between to_date(‘2018/06/27‘, ‘YYYY/MM/DD‘) and to_date(‘2019/07/27‘, ‘YYYY/MM/DD‘)
or to_date(‘2019/07/27‘, ‘YYYY/MM/DD‘) between to_date(begin_time) and to_date(end_time);
a ： to_date(begin_time)
b ：to_date(end_time)
c ：to_date(‘2018/06/27‘, ‘YYYY/MM/DD‘)
d ：to_date(‘2019/07/27‘, ‘YYYY/MM/DD‘)
原文地址：https://www.cnblogs.com/hq233/p/12199676.html