Try the following. Sorry we do not provide coding assistance here outside of simple examples. If still not working please contact a SQL expert to help you.
Code:
MONTH( `FIELD_NAME` ) = MONTH( NOW() ) AND DAY( `FIELD_NAME` ) = DAY( NOW() )
You must replace FIELD_NAME with the actual name of your field. So if the name of your field is cb_birthday then your query would be as follows.
Code:
MONTH( `cb_birthday ` ) = MONTH( NOW() ) AND DAY( `cb_birthday ` ) = DAY( NOW() )
This expects cb_birthday to be a Date fieldtype.