myql.db mysql.user

grant select on db01.* to testuser@"%"; will insert/modify records in the myql.db table

 

grant select on *.* to testuser@"%"; will not insert records in mysql.db, only modify the information in the mysql.user table

 

The value of Select_priv and Insert_priv in the mysql.db table is either Y or N

 

When the user is dropped, the relevant information in the mysql.db table will be deleted synchronously.