mysql

This is the situation:
You have two drupal sites which each a database. Your hosting allows only one database.
This is your solution:
Prefixing!

Rename all the tables in one of your databases to prefix_TABLENAME.
Follow this procedure to rename tables:
Type the mysql statement

show tables

When installing a xampp on mac os Mysql could throw an error #1153 - Got a packet bigger than 'max_allowed_packet' bytes
Solution : Extend the max_allowed_packet size located in Application/Xampp/xamppfiles/etc/my.cnf

On windows systems the file is called my.ini
On linux systems it is also my.cnf

Problem: You want to know the next id for the nodes. According to drupal you should use db_last_insert('table', 'field'). It returned allways zero for me. In essence the drupal function will execute SELECT LAST_INSERT_ID() in mysql. Even when I executed this directly in phpmyadmin is still returned 0 while my nid count was 20.