私は、データベースの専門家ではないが、私は私の理解が何であるかからのご質問にお答えしようとすることができます。
1)45 p/monthですか?
No, the max_connections is not per month but the number of concurrent
connections allowed simultaneously.
2)誰かが1つの接続を定義する理由を説明できますか?それはデータベースへのクエリですか?
3)クエリの場合、クエリで100個の値が返されるとどうなりますか?それらは接続としてカウントされますか?
The value returned by the query doesn't matter. It can return as many values as it
like(you need to handle that in your code though). What happens in the code is that
you open a connection and then run a query after that you close that connection.
What happens between when the connection open and closes doesn't affect the number
of connection.
However you need to take care of other parameters while running a long query into a
database. As it could spike your CPU/memory utilization etc. but the number of
connection per query would still be 1.