Fetch Similar Columns From Two Tables?

I am using this query to search checkbox values.

SqlCommand cmd = new SqlCommand("Select * from Details where Emp_Code in (" + selectedValues + ")", con);

I want to join a table called Materials to this now. Material table also has an Emp_Code column. How can I write a select sql query to fetch Emp_Code from both Details and Materials table.

SqlCommand cmd = new SqlCommand("select D.Emp_Code, M.Emp_Code from Details D, Materials M where D.Emp_Code = M.Emp_Code in (" + selectedValues + ")", con);