📝 Clarify description of in-memory SQLite database in `docs/tutorial/…

…create-db-and-table.md` (#601)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

docs/tutorial/create-db-and-table.md

@@ -220,7 +220,7 @@ Each supported database has it's own URL type. For example, for **SQLite** it is
 * `sqlite:///databases/local/application.db`
 * `sqlite:///db.sqlite`
 
-For SQLAlchemy, there's also a special one, which is a database all *in memory*, this means that it is deleted after the program terminates, and it's also very fast:
+SQLite supports a special database that lives all *in memory*. Hence, it's very fast, but be careful, the database gets deleted after the program terminates. You can specify this in-memory database by using just two slash characters (`//`) and no file name:
 
 * `sqlite://`