I was having trouble with a mysql account, and I eventually narrowed it down to the user's password, which contained the substring '\Y'.
If I create a user with that password, I can't log in with it:
mysql> create user 'test'@'localhost' identified by '\Y';
Query OK, 0 rows affected (0.00 sec)
mysql> exit
Bye
$ mysql -u test -p
Enter password:
ERROR 1045 (28000): Access denied for user 'test'@'localhost' (using password: YES)
This happens on two different machines and two different mysql versions.
mysql Ver 14.14 Distrib 5.5.37, for debian-linux-gnu (x86_64) using readline 6.3
mysql Ver 14.14 Distrib 5.6.19, for osx10.9 (x86_64) using EditLine wrapper
Any clues why this is happening?
The sequence '\Y' when you created the user is simply 'Y'. So that user's password is "Y".
In MySQL string literals, only certain backslash-codes have any special meaning. "\n" for example is a newline. When you put a backslash before most characters, it has no special meaning, it's just the same literal character. So a "\Y" is simply "Y".
If you want a literal backslash as part of the password, you need to escape the backslash. So to create a password that is the two characters "\Y" you need to:
mysql> create user 'test'@'localhost' identified by '\\Y';
Then when you type the password, use one backslash. Backslash has no meaning at all when typing passwords interactively, so there is no need to escape it.