SQL FIRST_VALUE() and LAST_VALUE()

FIRST_VALUE (), one of our new analytic functions that comes with SQL Server 2012, returns the first value in the sorted data set. LAST_VALUE () returns the last value in the sorted data set.

SELECT  cus.customer_id,cus.first_name, cus.last_name, 
	FIRST_VALUE(customer_id) OVER (PARTITION BY cus.first_name ORDER BY cus.first_name) 
	as  [first value]
FROM BikeStores.sales.customers as cus

---

SELECT  cus.customer_id,cus.first_name, cus.last_name, 
	LAST_VALUE(customer_id) OVER (PARTITION BY cus.first_name ORDER BY cus.first_name)
	as [last value]
FROM BikeStores.sales.customers as cus

---

SELECT  cus.customer_id,cus.first_name, cus.last_name, 
	FIRST_VALUE(customer_id) OVER (PARTITION BY cus.first_name ORDER BY cus.first_name) 
	as  [first value],
	LAST_VALUE(customer_id) OVER (PARTITION BY cus.first_name ORDER BY cus.first_name)
	as [last value]
FROM BikeStores.sales.customers as cus