Reverse order of a XML Column in SQL Server - sql-server

Question

In a SQL Server table, I have a XML column where status are happened (first is oldest, last current status).
I have to write a stored procedure that returns the statuses: newest first, oldest last.
This is what I wrote:
ALTER PROCEDURE [dbo].[GetDeliveryStatus]
#invoiceID nvarchar(255)
AS
BEGIN
SET NOCOUNT ON;
DECLARE #xml xml
SET #xml = (SELECT statusXML
FROM Purchase
WHERE invoiceID = #invoiceID )
SELECT
t.n.value('text()[1]', 'nvarchar(50)') as DeliveryStatus
FROM
#xml.nodes('/statuses/status') as t(n)
ORDER BY
DeliveryStatus DESC
END
Example of value in the statusXML column:
<statuses>
<status>A</status>
<status>B</status>
<status>A</status>
<status>B</status>
<status>C</status>
</statuses>
I want the procedure to return:
C
B
A
B
A
with ORDER BY .... DESC it return ALPHABETIC reversed (C B B A A)
How should I correct my procedure ?

Answer 1

Create a sequence for the nodes based on the existing order then reverse it.
WITH [x] AS (
SELECT
t.n.value('text()[1]', 'nvarchar(50)') as DeliveryStatus
,ROW_NUMBER() OVER (ORDER BY t.n.value('..', 'NVARCHAR(100)')) AS [Order]
FROM
#xml.nodes('/statuses/status') as t(n)
)
SELECT
DeliveryStatus
FROM [x]
ORDER BY [x].[Order] DESC
... results ...
DeliveryStatus
C
B
A
B
A

Answer 2

There is no need to declare a variable first. You can (and you should!) read the needed values from your table column directly. Best was an inline table valued function (rather than a SP just to read something...)
Better performance
inlineable
You can query many InvoiceIDs at once
set-based
Try this (I drop the mock-table at the end - carefull with real data!):
CREATE TABLE Purchase(ID INT IDENTITY,statusXML XML, InvocieID INT, OtherValues VARCHAR(100));
INSERT INTO Purchase VALUES('<statuses>
<status>A</status>
<status>B</status>
<status>A</status>
<status>B</status>
<status>C</status>
</statuses>',100,'Other values of your row');
GO
WITH NumberedStatus AS
(
SELECT ID
,InvocieID
, ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) AS Nr
,stat.value('.','nvarchar(max)') AS [Status]
,OtherValues
FROM Purchase
CROSS APPLY statusXML.nodes('/statuses/status') AS A(stat)
WHERE InvocieID=100
)
SELECT *
FROM NumberedStatus
ORDER BY Nr DESC
GO
--Clean-Up
--DROP TABLE Purchase;
The result
+---+-----+---+---+--------------------------+
| 1 | 100 | 5 | C | Other values of your row |
+---+-----+---+---+--------------------------+
| 1 | 100 | 4 | B | Other values of your row |
+---+-----+---+---+--------------------------+
| 1 | 100 | 3 | A | Other values of your row |
+---+-----+---+---+--------------------------+
| 1 | 100 | 2 | B | Other values of your row |
+---+-----+---+---+--------------------------+
| 1 | 100 | 1 | A | Other values of your row |
+---+-----+---+---+--------------------------+