multiple database in elgg

Hi evryone, just wanna ask if anyone of you could help me with my database problem. My problem is that I have 2 databases and I would like to sync them together, not combined them into 1 database but I just wanna access those 2 databases in one site, and I don't have any idea how.

e.g. my elgg database is "myelgg_db" den I have another one say "my_db", "my_db" is already an existing database for sometime now and the "myelgg_db" is just new.Then I copy some users from my "my_db" to my "myelgg_db" synchornizing them through "my_db.user.userid" and "myelgg_db.users_entity.guid" . Then I have a table "scores" in "my_db", I kinda would like to have them appear in my elgg site, so I have to query "my_db.scores" table in elgg. how do i do tha in elggt?

 

databasename: my_db

table1: user (userid, name, address,...)

table2: score (userid, score, daterated)

 

databasename: myelgg_db

table1: user_entity (guid,name, username)