TSQL Finding Order that occurred in 3 consecutive months

Question

Please help me to generate the following query. Say I have customer table and order table.

Customer Table

CustID CustName

1      AA     
2      BB
         


        

Answer 1

Here you go:

select distinct
 CustName
,year(OrderDate) [Year]
,OrderDate
from 
(
select 
 o2.OrderDate [prev]
,o1.OrderDate [curr]
,o3.OrderDate [next]
,c.CustName
from [order] o1 
join [order] o2 on o1.CustId = o2.CustId and datediff(mm, o2.OrderDate, o1.OrderDate) = 1
join [order] o3 on o1.CustId = o3.CustId and o2.OrderId <> o3.OrderId and datediff(mm, o3.OrderDate, o1.OrderDate) = -1
join Customer c on c.CustId = o1.CustId
) t
unpivot
(
    OrderDate for [DateName] in ([prev], [curr], [next])
)
unpvt
order by CustName, OrderDate