Merging tables

I am relatively new to R and am trying to do some basic data manipulation.  Basically I have a table (csv - table 1) of data for a set of samples (rows), and a second table (table 2) of information about a subset of samples of particular interest.  I want to pull out the data from table 1 for the samples in table 2, either by:
*       Merging the two tables based on a common identifier (SampleID - may have a different header in the two tables), and filter for overlapping entries (preferred approach)
*       OR filter table 1 for entries where SampleID matches to one in a list taken from table 2

Any help would be gratefully recieved.

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