In bigger organizations, the data in a table might be sensitive to few departments but not the others. Some people may need to rows from the table that belongs to few departments where another group of people may need to access the data belongs to another few departments in one table. Those 2 groups of people might share the data from one or few departments. Implementing such logics is not a big deal for customized applications, for instance use procedures to filter rows out. What if users access data using very genaric tools, such as SSMS, in which they can arbitrarily issue queries against table. How would you selectively return rows from a table without asking uses putting filters in their queries?