Concatenating multiple result rows into a single result without using FOR XML PATH
I've inherited a stored procedure that uses FOR XML PATH in a subselect to concatenate multiple result rows from the subselect into a single result column on the "main" query. Consider the following, where table "z" is part of the main query's FROM clause:
SELECT SUBSTRING((SELECT ('; ' + RTRIM(c.SomeField))
FROM a (NOLOCK)
INNER JOIN b (NOLOCK) ON a.aid = b.aid
INNER JOIN c (NOLOCK) ON b.cid = c.cid
WHERE a.zid = z.zid
FOR XML PATH('')), 3, 1000)
This returns the following, if there were three result rows from the subselect:
value1; value2; value3
Most of the time, this works great. However, several of the values for c.SomeField
, which is a varchar, have special XML characters in them, most frequently the ampersand. So, when one of the values has an ampersand, I get this:
value1 & 开发者_StackOverflow中文版more value1; value2; value3
Is there another way I can concatenate these row results together? If not, is there a simple way to decode the string in .NET?
From MVP Rob Farley:
SELECT SUBSTRING((
SELECT ('; ' + RTRIM(c.SomeField))
FROM a (NOLOCK)
INNER JOIN b (NOLOCK) ON a.aid = b.aid
INNER JOIN c (NOLOCK) ON b.cid = c.cid
WHERE a.zid = z.zid
FOR XML PATH(''), ROOT('xml'), TYPE
).value('/xml[1]','varchar(max)'), 3, 1000)
He points out:
However, if I actually make my FOR XML call return actual well-formed XML, then I can extract the contents out, and it returns the data to me in its original (correct) form.
You can run these statements as one batch to get what you want:
declare @s as varchar(max);
select @s = isnull(@s + '; ', '') + SomeField
from (
SELECT RTRIM(c.SomeField) as SomeField
FROM a (NOLOCK)
INNER JOIN b (NOLOCK) ON a.aid = b.aid
INNER JOIN c (NOLOCK) ON b.cid = c.cid
WHERE a.zid = z.zid
) a;
select @s as SomeFieldList;
Update: here is a proof of concept without using your schema:
declare @s as varchar(max);
select @s = isnull(@s + '; ', '') + SomeField
from (
SELECT 'aaa' as SomeField
UNION ALL
SELECT 'bbb'
UNION ALL
SELECT 'ccc'
) a;
select @s as SomeFieldList;
精彩评论