Concatenate table of two columns into a single string with 2 delimiters - tsql

Question

Let's say I have a table with two columns:
create table #counties(
state varchar(max),
name varchar(max)
)
insert #counties(state,name) values('Alabama','Autauga')
insert #counties(state,name) values('Alabama','Baldwin')
insert #counties(state,name) values('Texas','Adams')
insert #counties(state,name) values('Texas','Houston')
insert #counties(state,name) values('Wisconsin','Adair')
insert #counties(state,name) values('Wisconsin','Wood')
I'd like the result to be a single string like this:
Autauga;Baldwin^^Adams;Houston^^Adair;Wood
For each change in the first column, I'd like the ^^ delimiter, and for each change in the second column, I'd like the ; delimiter.
I'm aware of the coalesce function but I can't figure out how to use it over two columns, not just one:
declare #c varchar(max)
select #c = COALESCE(#c + ';', '') + name from #counties order by state, name
select #c
This is just for a data load but I'd still like to learn how to do it elegantly with just a select, and hopefully without a cursor loop.

Answer 1

Try it like this
With NamesPerState AS
(
SELECT c1.[state]
,STUFF(
(
SELECT ';' + c2.[name]
FROM #counties AS c2
WHERE c1.[state]=c2.[state]
ORDER BY c2.[name]
FOR XML PATH('')
),1,1,'') AS names
FROM #counties AS c1
GROUP BY c1.[state]
)
SELECT STUFF
(
(
SELECT '^^' + names
FROM NamesPerState
ORDER BY [state]
FOR XML PATH('')
),1,2,''
)
UPDATE
Just to show you, how easy this was with a clean and modern approach:
SELECT [state]
,
(
SELECT c2.[name]
FROM #counties AS c2
WHERE c1.[state]=c2.[state]
ORDER BY c2.[name]
FOR XML RAW('county'),TYPE
)
FROM #counties AS c1
GROUP BY c1.[state]
FOR XML RAW('state'),ROOT('counties')
The result
<counties>
<state state="Alabama">
<county name="Autauga" />
<county name="Baldwin" />
</state>
<state state="Texas">
<county name="Adams" />
<county name="Houston" />
</state>
<state state="Wisconsin">
<county name="Adair" />
<county name="Wood" />
</state>
</counties>
UPDATE 2 Just for fun: the minimal output
SELECT [state] AS [*]
,
(
SELECT c2.[name] AS [*]
FROM #counties AS c2
WHERE c1.[state]=c2.[state]
ORDER BY c2.[name]
FOR XML PATH('c'),TYPE
)
FROM #counties AS c1
GROUP BY c1.[state]
FOR XML PATH('s'),ROOT('counties')
The result
<counties>
<s>Alabama<c>Autauga</c><c>Baldwin</c></s>
<s>Texas<c>Adams</c><c>Houston</c></s>
<s>Wisconsin<c>Adair</c><c>Wood</c></s>
</counties>
And this would get your list back:
DECLARE #x XML=
'<counties>
<s>Alabama<c>Autauga</c><c>Baldwin</c></s>
<s>Texas<c>Adams</c><c>Houston</c></s>
<s>Wisconsin<c>Adair</c><c>Wood</c></s>
</counties>';
SELECT s.value('(text())[1]','nvarchar(max)') AS [state]
,c.value('.','nvarchar(max)') AS [name]
FROM #x.nodes('/counties/s') AS A(s)
OUTER APPLY s.nodes('c') AS B(c)