How should I modify this SQL statement? - sql

Question

My SQL Server view
SELECT
geo.HyperLinks.CatID, geo.Tags.Tag, geo.HyperLinks.HyperLinksID
FROM
geo.HyperLinks LEFT OUTER JOIN
geo.Tags INNER JOIN
geo.TagsList ON geo.Tags.TagID = geo.TagsList.TagID ON geo.HyperLinks.HyperLinksID = geo.TagsList.HyperLinksID WHERE HyperLinksID = 1
returns these...
HyperLinksID CatID Tags
1 2 Sport
1 2 Tennis
1 2 Golf
How should I modify the above to have results like
HyperLinksID CatID TagsInOneRowSeperatedWithSpaceCharacter
1 2 Sport Tennis Golf
UPDATE: As Brad suggested I came up here...
DECLARE #TagList varchar(100)
SELECT #TagList = COALESCE(#TagList + ', ', '') + CAST(TagID AS nvarchar(100))
FROM TagsList
WHERE HyperLinksID = 1
SELECT #TagList
Now the result looks like
HyperLinksID CatID TagsInOneRowSeperatedWithSpaceCharacter
1 2 ID_OF_Sport ID_OF_Tennis ID_OF_Golf
And of course I have to combine the contents from the#TagList variable and the original SELECT statement...
Which means that I'll have to wait for the holy SO bounty :(

Answer 1

If SQL, try this post:
Concatenating Row Values
If you want to try your hand at CLR code, there are examples of creating a custom aggregate function for concatenation, again, for MS SQL.
This post is pretty exhaustive with lots of ways to accomplish your goal.

Answer 2

Using the approach from here to avoid any issues if your tag names contain special XML characters:.
;With HyperLinks As
(
SELECT 1 AS HyperLinksID, 2 AS CatID
),
TagsList AS
(
SELECT 1 AS TagId, 1 AS HyperLinksID UNION ALL
SELECT 2 AS TagId, 1 AS HyperLinksID UNION ALL
SELECT 3 AS TagId, 1 AS HyperLinksID
)
,
Tags AS
(
SELECT 1 AS TagId, 'Sport' as Tag UNION ALL
SELECT 2 AS TagId, 'Tennis' as Tag UNION ALL
SELECT 3 AS TagId, 'Golf' as Tag
)
SELECT HyperLinksID,
CatID ,
(SELECT mydata
FROM ( SELECT Tag AS [data()]
FROM Tags t
JOIN TagsList tl
ON t.TagId = tl.TagId
WHERE tl.HyperLinksID = h.HyperLinksID
ORDER BY t.TagId
FOR XML PATH(''), TYPE
) AS d ( mydata ) FOR XML RAW,
TYPE
)
.value( '/row[1]/mydata[1]', 'varchar(max)' ) TagsInOneRowSeperatedWithSpaceCharacter
FROM HyperLinks h
Edit: As KM points out in the comments this method actually automatically adds spaces so I've removed the manually added spaces. For delimiters other than spaces such as commas Peter's answer seems more appropriate.
If you know your data will not contain any problematic characters then a simpler (probably more performant) version is
SELECT CatID ,
HyperLinksID,
stuff(
( SELECT ' ' + Tag
FROM Tags t
JOIN TagsList tl
ON t.TagId = tl.TagId
WHERE tl.HyperLinksID = h.HyperLinksID
ORDER BY t.TagId
FOR XML PATH('')
), 1, 1, '') TagsInOneRowSeperatedWithSpaceCharacter
FROM HyperLinks h

Answer 3

Use FOR XML in a correlated subquery. For a space-delimited list:
SELECT h.HyperLinksID, h.CatID
, TagList = (
SELECT t.Tag AS [data()]
FROM geo.TagList l
JOIN geo.Tags t ON l.TagId = t.TagId
WHERE l.HyperLinksID = h.HyperLinksID
ORDER BY t.Tag
FOR XML PATH(''), TYPE
).value('.','NVARCHAR(MAX)')
FROM geo.HyperLinks AS h
WHERE h.HyperLinksID = 1
For any other delimiter:
SELECT h.HyperLinksID, h.CatID
, TagList = STUFF((
SELECT ', '+t.Tag
FROM geo.TagList l
JOIN geo.Tags t ON l.TagId = t.TagId
WHERE l.HyperLinksID = h.HyperLinksID
ORDER BY t.Tag
FOR XML PATH(''), TYPE
).value('.','NVARCHAR(MAX)')
,1,2,'')
FROM geo.HyperLinks AS h
WHERE h.HyperLinksID = 1
The subquery creates a delimited list, and then STUFF(...,1,2,'') removes the leading ,. TYPE).value() gets around most common problems w/ special characters in XML.