选择所有列值相同的行

Question

I have a table of users.

I want to send emails of 'latest matches' - where a match is when two users live in the same country.

This will be done by a cron job - not for each specific user when they are logged in.

The script needs to do this as a 'spectator' of the whole database.

How do I select all users with the same location? Not by giving a value.

Not:

"SELECT * FROM users WHERE location = 'Germany';

But:

"SELECT * FROM users WHERE something something something // where location is the same.

So that the query returns all users from germany in one group/array, all users from france in one group/array etc.

Also, if I'm not being too cheeky asking two in one, is there anything different in the way you handle the result in this type of query? As There would be multiple arrays? Would it return one multi-dimensional array, which I can then choose to have returned as associative?

Thanks

Answer 1

select location, group_concat(user_name) as users
from users
group by location

or simply iterate over the result that is ordered by location

select user_name
from users
order by location, username