SQL Server: Select Top 0?

Its a way of getting an empty set; for example to create a new empty table with the same columns as an existing one;

SELECT TOP 0 * INTO new_table FROM old_table

Or to act a as source for column names
Or as a way to return column details but no data to a client layer
Or as a query to check connectivity

Its the same as;

SELECT * FROM table WHERE 0=1