sql如何将一次查询的结果与另一次查询的结果合并并排序

Question

查询1：
Select null as name,Checkinout.* from Checkinout where (Checkinout.userid=1000000000000 and (Checkinout.CheckTime >='2008-01-01 00:00:00') and (Checkinout.CheckTime <='2020-01-01 23:59:59')) Order By Checkinout.CheckTime DESC Limit '0','6'

查询2：
Select UserInfo.name,Checkinout.* from UserInfo left join Checkinout on Checkinout.userid=UserInfo.userid where ((Checkinout.CheckTime >='2008-01-01 00:00:00') and (Checkinout.CheckTime <='2020-01-01 23:59:59')) Order By Checkinout.CheckTime DESC Limit '0','6'

将这两次查询的结果合并后按照Checkinout.CheckTime排序

Answer 1

Select null as name,Checkinout.* from Checkinout where (Checkinout.userid=1000000000000 and (Checkinout.CheckTime >='2008-01-01 00:00:00') and (Checkinout.CheckTime <='2020-01-01 23:59:59')) Order By Checkinout.CheckTime DESC Limit '0','6'
UNION
Select UserInfo.name,Checkinout.* from UserInfo left join Checkinout on Checkinout.userid=UserInfo.userid where ((Checkinout.CheckTime >='2008-01-01 00:00:00') and (Checkinout.CheckTime <='2020-01-01 23:59:59')) Order By Checkinout.CheckTime DESC Limit '0','6'
ORDER BY CheckTime;