The default [db] entry in the protected/config/main.php is a sqlite entry; there is a commented-out entry for mysql. In that entry, the host is written as ‘localhost’. However this failed on my installation (Yii 1.1.9.r3527, MySql 5.5.12, Mac OS X 10.6.8 ). Changing the entry to use 127.0.0.1 for the loopback connection fixed things.
AD