Understanding the recursive CTE termination check

Question

In this sqlfiddle...

http://sqlfiddle.com/#!6/b6587/6

I am getting the following error....

The statement terminated. The maximum recursion

Answer 1

Here's a better example using dates. Assume we want to build a table of dates. 1 row for every month for the year 2017. We create a @startDate as the anchor and @endDate as the terminator. We set these to 12 months apart, since we want a single year. Then, the recursion will add one month via the DATEADD function to the @startDate until the terminator is met in the WHERE clause. We know it will take 11 recursions to hit 12 months... that is, 11 months + the start date. If we set the MAXRECURSION to anything less than 11, then it will fail since 11 are needed to fulfill the WHEREclause in our recursive CTE, that is the terminator..

declare @startDate datetime = '20170101'
declare @endDate datetime = '20171201'

;WITH Months
as
(
    SELECT @startDate as TheDate       --anchor
    UNION ALL
    SELECT DATEADD(month, 1, TheDate)  --recursive
    FROM Months
    WHERE TheDate < @endDate           --terminator... i.e. continue until this condition is met

)


SELECT * FROM Months OPTION (MAXRECURSION 10) --change this to 11

For your query, a simple join would suffice.

select 
  firstName
  ,lastName
  ,orderDate
  ,productID
from
  customers c
inner join
  orders o on o.customerID = c.id

However, I see that you are trying to return this in an odd format, which should be handled in what ever reporting application you are using. This would get you close without recursion.

with cte as(
select 
  firstName
  ,lastName
  ,orderDate
  ,productID
  ,dense_rank() over(order by c.id) as RN
from
  customers c
inner join
  orders o on o.customerID = c.id)


select distinct
  firstName
  ,lastName
  ,null
  ,null
  ,RN
from 
  cte
union all
select
  ''
  ,''
  ,orderDate
  ,productID
  ,RN
from 
  cte
order by RN, firstName desc