Well it depends. Are the tables related? Are you writing a measure or a calc column? Why do you want to do this - IE what are you trying to achieve and why?
Ok, you assuming you are writing a measure over your data table, you can use the RELATED() function to do what you want. https://msdn.microsoft.com/en-us/library/ee634202.aspx
If you are writing a measure over a lookup table, there is a RELATEDTABLE function, but this may be an issue as it will return multiple rows of data.
If these two tables are related, you can use LOOKUPVALUE() function to import the expected column into current table based on the related column. And concatenate it with existing column.
Then involve this calculated column in your measure.
LOOKUPVALUE Function (DAX)