MySQL ERRO: Not connected while trying to connect via command line

Use this query:

SELECT User FROM mysql.user;

Which will output a table like this:

+-------+
| User  |
+-------+
| root  |
+-------+
| user2 |
+-------+

As Matthew Scharley points out in the comments on this answer, you can group by the User column if you'd only like to see unique usernames.

I think one can end up in this position with older versions of mysql already installed. I had the same problem and none of the above solutions worked for me. I fixed it thus:

Used brew's remove & cleanup commands, unloaded the launchctl script, then deleted the mysql directory in /usr/local/var, deleted my existing /etc/my.cnf (leave that one up to you, should it apply) and launchctl plist

Updated the string for the plist. Note also your alternate security script directory will be based on which version of MySQL you are installing.

Step-by-step:

brew remove mysql

brew cleanup

launchctl unload -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist

rm ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist

sudo rm -rf /usr/local/var/mysql

I then started from scratch:

1. installed mysql with brew install mysql

2. ran the commands brew suggested: (see note: below)

   unset TMPDIR
   
   mysql_install_db --verbose --user=`whoami` --basedir="$(brew --prefix mysql)" --datadir=/usr/local/var/mysql --tmpdir=/tmp
   

3. Start mysql with mysql.server start command, to be able to log on it

4. Used the alternate security script:

   /usr/local/Cellar/mysql/5.5.10/bin/mysql_secure_installation
   

5. Followed the launchctl section from the brew package script output such as,

   #start
   launchctl load -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
   
   #stop
   launchctl unload -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
   

Note: the --force bit on brew cleanup will also cleanup outdated kegs, think it's a new-ish homebrew feature.

Note the second: a commenter says step 2 is not required. I don't want to test it, so YMMV!