normal use

win system keyboard shortcut to lock the system：win+L

transfer the direction of window scree: Ctrl+shfit+上下左右

Excel keyboard shortcut to replace sth with sth：Ctrl+H

 

The sql statement to remove the duplicate record from the table in database is that:

    delete from (select *,row_number() over(partition by id,name,age.....) from user) where row_number <>1;

there are two tables A and B, and all the fields are same.

    to select the data in table A but not in table B:

        select * from A left join B on A.id=B.id where B.name is null;

   to select the data in table B but not in table A:  

        select * from B left join A on A.id=B.id where A.name is null;