Need to locate customers who has placed their orders twice in a certain period. Now, the order might not be exactly the same, thus cant use a normal query finding duplications, but rather compare the order values of a customer and indicate the orders whose values differ with about 20%..
the simplest would be
the simplest would be
select t1.customerid,t1.orderid,t1.ordervalue ,t2.ordervalue
from Table1 as T1
join Table1 as T2
on t1.orderid <> t1.orderid
and t1.customerid = t2.customerid
and t1.ordervalue < t2.ordervalue * 1.2
and t1.ordervalue > t2.ordervalue * .8