Groups , sum ,inner join How to do it ??

Hello , i'm new and i want your help guys! I've 3 tables with one common field (id) .
the data look like this ..
companyid |datetrn |income| expenses | tax income | tax expenses |..
01 |2012/01/01|100 | 0 | 0 | 10 |..
02 |2012/02/15|0 | 150 | 12 | 0 |..
03 |2012/03/20|1500 | 1000 | 0 | 100 |..

so here start the troubles .. I want to join those 3 tables with id (ok with this) and present results like the following ..

inc. sum|exp.sum|tot.period|in.tax sum|ex.tax sum|tot.period
january | 100 | 0 | 100 | 0 | 10 | 10
february | 0 | 150 | 50 | 12 | 0 | -2
march | 1000 | 0 | 1050 | 0 | 100 | 98
........

Is this possible ?

thanks in advance !

I am not exactly getting where you have problem ...

for getting the month name you can use --

EXTRACT(MONTH FROM d) for mysql
or

TO_CHAR(d, 'MON') -> Three character month for oracle

d is the date field