I want to design a query to compute some returns for stock data and in searching the 'SQL Server Books Online' I find a very small and not so helpful at all help section on the lead and lag functions.

Part I of this series introduced the lead/lag control strategy as it applies to parallel pump operation and discussed the need for identifying the designer’s intent for a particular system. Part II ...

i. Lead secondary chilled water pump will be enabled anytime the chilled water (CHW) system is enabled and will remain enabled for 30 minutes after the CHW system is disabled. b. Pump speed control i.