Concatenating row values using Inner Join - sql

Question

I have this query that I'm using to join two tables for an update statement. This is the query that I built:
DECLARE #DocHoldReasons VARCHAR(8000)
SET #DocHoldReasons = 'DocType Hold'
UPDATE dbo.EpnPackages
SET Error = 1, Msg = COALESCE (#DocHoldReasons + ': ', '') + cv.Value
FROM EpnPackages p
INNER JOIN EpnCountyValues cv ON cv.CountyId = p.CountyId and cv.ValueName = 'DocHoldReason'
WHERE p.Status = 1000
AND p.Error = 0
There are two rows in the EpnCountyValues table with the same ValueName, and I need them both concatenated, and I'm having a tough time doing it. All I can get is the first row value. This is what my resulting string should look like - 'DocType Hold: Test: Test.124.'
eidt: I need the rows with the same ValueName to be concatenated for the update query. There could be more than two rows with ValueName = DocHoldReason
Here's the structure of the EpnCountyValues table:
CountyValueId CountyId ValueName Value
1 1 DocHoldReason Test
2 2 xyz Test1
3 3 DocHoldReason Test.124.
Any help would be greatly appreciated. Thanks!

Answer 1

You can do what you want by pre-aggregating the table before the join. If there are only two values and you don't care about the order, then this will work:
DECLARE #DocHoldReasons VARCHAR(8000);
SET #DocHoldReasons = 'DocType Hold';
UPDATE dbo.EpnPackages
SET Error = 1,
Msg = (COALESCE(#DocHoldReasons + ': ', '') + minv +
(case when minv <> maxv then ': ' + maxv else '' end)
)
FROM EpnPackages p INNER JOIN
(select cv.CountyId, min(cv.value) as minv, max(cv.value) as maxv
from EpnCountyValues cv
where cv.ValueName = 'DocHoldReason'
) cv
ON cv.CountyId = p.CountyId
WHERE p.Status = 1000 AND p.Error = 0;
EDIT:
For more than two values, you have to do string concatenation. That is "unpleasant" in SQL Server. Here is the approach:
DECLARE #DocHoldReasons VARCHAR(8000);
SET #DocHoldReasons = 'DocType Hold';
UPDATE dbo.EpnPackages
SET Error = 1,
Msg = (COALESCE(#DocHoldReasons + ': ', '') +
stuff((select ': ' + cv.value
from EpnCountyValues cv
where cv.ValueName = 'DocHoldReason' and
cv.CountyId = p.CountyId
for xml path ('')
), 1, 2, '')
)
WHERE p.Status = 1000 AND p.Error = 0;
This version does it using a correlated subquery rather than a join with an aggregation.
EDIT II:
You can fix this with an additional coalesce:
DECLARE #DocHoldReasons VARCHAR(8000);
SET #DocHoldReasons = 'DocType Hold';
UPDATE dbo.EpnPackages
SET Error = 1,
Msg = (COALESCE(#DocHoldReasons + ': ', '') +
COALESCE(stuff((select ': ' + cv.value
from EpnCountyValues cv
where cv.ValueName = 'DocHoldReason' and
cv.CountyId = p.CountyId
for xml path ('')
), 1, 2, ''), '')
)
WHERE p.Status = 1000 AND p.Error = 0;

Answer 2

You can join the EpnCountyValues table twice!
Something like this,
DECLARE #DocHoldReasons VARCHAR(8000)
SET #DocHoldReasons = 'DocType Hold'
Select #DocHoldReasons + ': ' + ev1.Value + ': ' + ev2.Value
From EpnPackages p
Join EpnCountyValues ev1 on p.packageID = ev1.packageID
Join EpnCountyValues ev2 on ev1.ValueName = ev2.ValueName
Where ev1.ValueName = 'DocHoldRegion'
And p.status = 1000
And p.error = 0
Does that select look right to you? If so, run the update. I always try to run a select before an update. I have to admit, I'm a bit confused why you're joining on CountyID, but then it seems like you'll be updating the values from different counties?