Including CTE within a query - sql

Question

I have the following code which works perfectly.
What I need to do is include it in a query using the result of the CTE as a column in the query result but I cannot work out the way to include it.
Any ideas please?
What I would like is effectively this:
select a,
b,
c,
d,
WITH invoicedates AS (
SELECT
ROW_NUMBER() OVER (ORDER BY Inv_Date DESC) AS RowNumber,
inv_Date, INVIT_PARTNO
FROM Invoices join InvoiceItems on invit_invno = inv_no
WHERE invit_partno = stock_no and inv_canind <> 'Y' and inv_date >= DATEADD(yy, -1, getdate())
)
SELECT
AVG(DATEDIFF(DD, O2.Inv_Date, O1.Inv_Date)) AS AverageFrequency
FROM invoicedates O1
LEFT JOIN invoicedates O2
ON O2.RowNumber = O1.RowNumber + 1
from stock where ..........
to give a resulting output of a b c d result

Answer 1

You should be able to just reorder how you're using the CTE:
; WITH invoicedates (RowNumber, inv_Date, INVIT_PARTNO) AS (
SELECT
ROW_NUMBER() OVER (ORDER BY Inv_Date DESC) AS RowNumber,
inv_Date, INVIT_PARTNO
FROM Invoices join InvoiceItems on invit_invno = inv_no
WHERE invit_partno = stock_no and inv_canind <> 'Y' and inv_date >= DATEADD(yy, -1, getdate())
)
select a,
b,
c,
d,
AVG(DATEDIFF(DD, O2.Inv_Date, O1.Inv_Date)) AS AverageFrequency
FROM invoicedates O1
LEFT JOIN invoicedates O2
ON O2.RowNumber = O1.RowNumber + 1