SQL concat rows with same ID and newest date - sql

Question

I'm looking for help querying the output of my application's messages. I have a query which takes lines of each message and concats them together to form a sentence. However some of my message numbers have two or more messages, in this case I only want the message with newest date. My current code outputs all messages in a sentence by concatenating line numbers together in order for each message number and outputting them in order by MSG_NUM. I've added ordering by MSG_START_DATE but as expected that still gives me both. How can I do a select max for each concatenated message line?
Here are the fields I'm working with:
MSG_NUM | MSG_START_DATE | MSG_LINE_NUM | MSG_TEXT
1 | 2010-01-15 | 1 | Invalid operation
1 | 2010-01-15 | 2 | try again
1 | 2014-02-21 | 1 | Invalid input
1 | 2014-02-21 | 2 | try again
Here is my current code:
Select distinct ST2.[MSG_NUM],
substring(
(
(Select ' '+LTRIM(RTRIM(ST1.[MSG_TEXT])) AS [text()]
From database..messages ST1
Where ST1.[MSG_NUM] = ST2.[MSG_NUM]
ORDER BY ST1.[MSG_START_DATE], ST1.[MSG_LINE_NUM]
For XML PATH (''),root('xmlchar'), type).value('/xmlchar[1]','varchar(max)')
), 2, 2000) [Message]
From database..messages ST2 order by ST2.[MSG_NUM]
And here is the output I receive:
1 Invalid operation try again Invalid input try again
I only want the output:
1 Invalid input try again
Any ideas on how I can do this?

Answer 1

What about you filtering by date ?
Select distinct ST2.[MSG_NUM],
substring(
(
(Select ' '+LTRIM(RTRIM(ST1.[MSG_LINE_NUM])) AS [text()]
From database..messages ST1
Where ST1.[MSG_NUM] = ST2.[MSG_NUM]
AND ST1.[MSG_START_DATE] = (SELECT MAX(ST3.[MSG_START_DATE])
FROM database..messages ST3
WHERE ST2.[MSG_NUM] = ST3.[MSG_NUM]
)
ORDER BY ST1.[MSG_LINE_NUM]
For XML PATH (''),root('xmlchar'), type).value('/xmlchar[1]','varchar(max)')
), 2, 2000) [Message]
From database..messages ST2 order by ST2.[MSG_NUM]
Better yet, just filter before passing to your query
WITH maxd
AS (
SELECT *
,MAX(MSG_START_DATE) OVER (PARTITION BY [MSG_NUM]) AS maxdate
FROM DATABASE..messages
)
,filter
AS (
SELECT *
FROM maxd
WHERE MSG_START_DATE = maxdate
)
SELECT DISTINCT ST2.[MSG_NUM]
,substring((
(
SELECT ' ' + LTRIM(RTRIM(ST1.[MSG_LINE_NUM])) AS [text()]
FROM filter ST1
WHERE ST1.[MSG_NUM] = ST2.[MSG_NUM]
ORDER BY ST1.[MSG_LINE_NUM]
FOR XML PATH('')
,root('xmlchar')
,type
).value('/xmlchar[1]', 'varchar(max)')
), 2, 2000) [Message]
FROM filter ST2
ORDER BY ST2.[MSG_NUM]