How to format cell values based on codes for other values?

Preemptive apology for bumbling through this question.  I have a master table with two columns containing (A) codes and then (B) street names that match each code, i.e. | 275197_5 | MAIN ST |.  I have reports that are generated containing various codes from column one in the master table, but the report does not produce the name of each street.  I want to make a column in the report that displays the proper street name based on the code that is generated in the report.  So if the report spits out 275197_5 in column 1, column 2 with display MAIN ST based on the values in the master table.  Thoughts?