How to write an SQL statement for sorting the release time and update time

There are two sorting fields, the update time: upTime release time: After the addTime article is published, there will be its release time. If you modify the article, a modification time will be saved. Sort data on the homepage according to the following rules: 1. If an article with an update time uses upTime, only the published time uses ad..., there are two sorting fields,
Update Time: upTime
Release date: addTime

An article will be published after it is published. If it is modified, a modification time will be saved.
Retrieve data on the homepage and sort the data according to the following rules:
1. For articles with Update time, use upTime and only addTime for release time for sorting in order

// The data retrieved in this way is not required. select * from table order by upTime desc, addTime desc

Reply content:

There are two sorting fields,
Update Time: upTime
Release date: addTime

An article will be published after it is published. If it is modified, a modification time will be saved.
Retrieve data on the homepage and sort the data according to the following rules:
1. For articles with Update time, use upTime and only addTime for release time for sorting in order

// The data retrieved in this way is not required. select * from table order by upTime desc, addTime desc

Select * from table order by case when upTime is null then addTime desc else upTime desc end

Maybe you have a problem with your thinking? I think it is dizzy.
At the first release of the articleaddTimeAndupTimeIsn't it? To retrieve data, you only need to useupTimeSorting is fine, because there is noupTimeNoupTimeIn the caseupTimeEqualaddTime.

UpTime = addTime

If not, add a field for sorting.