01. 00:00 Second subquery
See that a query can contain multiple subqueries and how to make difference between them.
02. 01:40 Division by zero
Understanding division by zero problem.
03. 02:00 Null behavior in formulas
Divisition by NULL is different then division by zero. Operations with NULL results NULL. This way division by null returns null instead of an error.
04. 03:24 Benefit of this method
See that this way sql queries run completely on server side and only result is returned to the client (in this case to SSMS).