MySQL: I omitted a space--what did I do?

Question

I'm curious and learning...this is non-urgent

On a production server running 19 databases I entered this typo

mysql -uroot-p[passwd]
            ^ omitted space

I soon enjoyed a solid 12 seconds of Shark-Eats-Quint-Grade elevated heart rate:

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| test               |
+--------------------+

I've confirmed this typo as harmless** but now am curious how this yielded output rather than error.

My SQL-Fu grows but is not yet very strong. I clearly attempted authentication with the unintentional user root-ppasswd, but with neither password passed to mysql nor existing true credentials I'd have expected the command to fail--did this spawn a new theoretical DB instance awaiting its chance to be permanently written?

** Please allow me to preempt those inclined to stress the danger of premature engagement with the <enter> key. Yes--hollowpoint ducked.

Answer 1

It's treating the whole string as the username and without a password the MySQL client is logging you in as anon.

mysql -usomerandomstring
mysql> SELECT CURRENT_USER();
+----------------+
| CURRENT_USER() |
+----------------+
| @localhost     |
+----------------+

Answer 2

update

I knew I'd risk learning something here. :-)

Didn't want to preclude upvotes on harvey's helpful answer but address fellow SQL noobs...

As harvey mentioned, I've tripped over anonymous login. My manual doesn't reference anonymous user--not that I read its entirety before posting or even knew what to seek, which is why web search quickly yielded to ServerFault.

I found this advice on removing anon login, coming soon to a non-work day near you:

DELETE FROM mysql.user WHERE User='';