[R] need help combining two datasets

[Somani, Dinesh K]

Hi 

I am a new R user.

I have two CSV files, one with daily stock returns using method A {date, stock, returnA, some uninteresting columns}, and another with method B {date, stock, returnB, more columns}. Both have different sets of stocks. 

I want to combine the two into a single data table, so that I can run some analyses for the overlapping date ranges and stocks. I know how to do this using a database but is there an equivalent way to perform a similar kind of join in R?

Data size is small - just a few years worth of daily data.

Would appreciate your help.

Thanks a lot
Dinesh