details as following:
When performing group by on a table without a primary key, the field following the group by must be able to uniquely identify a piece of data.
Otherwise, it will appear: the result is 1 or no result;
details as following:
When performing group by on a table without a primary key, the field following the group by must be able to uniquely identify a piece of data.
Otherwise, it will appear: the result is 1 or no result;