sub select statements?

hi there! i'm quite a newbie to php and pear, so please forgive me if this is too silly,but i haven't been able to get it working with the help of the documentation... i have to insert some mysql statements in an existing php file. this file belongs to a php-framework,so i could see how most things are done with the PEAR::DB class. but i experienced problem with one of my statements: INSERT INTO tablename SELECT some, columns FROM another_table LEFT JOIN third_table ON another_table.column=third_table.column WHERE another_table.id=somevalue; this thing produces an DB error: Unknown Error does anybody know something about this? do i have a wrong pear version? i can enter this statement in the mysql prompt and everything works out fine! thanks in advance udo