Mysql order by null

Today, I found in mysql that there is such a select * from bb order by null sentence that cannot be seen, later, I found out that order by null is used to forcibly disable sorting of query results.

Order by null is used to forcibly disable sorting of query results. When you use explain to check the query statement, if the Extra column contains Using filesort, this has a certain impact on the performance, especially when Using group by, even if you do not display the specified order, mysql sorts data by grouping fields by default. In some cases, there is no need to use sorting. For example, when processing table report data (insert the original table data to a table for REPORT query after data statistics ), you can use order by null to cancel sorting. For example:

The Code is as follows:	Copy code
Insert into reportTable (day, clicks, revenue) Select day, count (*), sum (revenue) from clickOriginTalbe Group by day Order by null

In Order by, where is the Null value of MySQL? .

A:

In ASC, null is at the beginning, and desc is at the end.