How to group a table, at the same time saving all column values in each group to a single column as comma-separated values - sql

Question

Please see the following SQL code.
Declare #LookUp table (id int,val varchar(12))
insert into #LookUp values (1,'A'),(1,'D'),(1,'X'),(2,'B'),(2,'F')
Declare #summary table (id int,val varchar(2000))
------------------------------
Declare #value varchar(30)
Declare #start int = 1, #end int = (Select count(Distinct id) from #LookUp)
While #start <= #end
Begin
Set #value = ''
Select #value = #value + '|' + val From #LookUp Where id = #start
Insert into #summary
Select #start,Right(#value,Len(#value)-1)
Set #start = #start + 1
End
Select * From #summary
With the following query, I am grouping based on Id, and making the values with in a group, as comma-separated values.
Input:
Output:
I have done this using a loop, which is not performing very well when it comes to large amount of data.
Can we do this avoiding a loop?
Note: Assume that #lookup.id is continuous.

Answer 1

INSERT #summary(id, val)
SELECT
t.id,
STUFF((
select '|' + [val]
from #LookUp t1
where t1.id = t.id
for xml path(''), type
).value('.', 'varchar(max)'), 1, 1, '') [values]
FROM #LookUp t
GROUP BY t.id

Answer 2

Try this..
Declare #LookUp table (id int,val varchar(12))
insert into #LookUp values (1,'A'),(1,'D'),(1,'X'),(2,'B'),(2,'F')
select
id,
val =
stuff((
select
'| ' + t2.val
from #LookUp t2
where
t2.id = t1.id
group by t2.val
for xml path(''), type).value('.', 'varchar(max)'
), 1, 2, '')
from #LookUp t1
GROUP BY t1.id

Answer 3

Declare #LookUp table (id int,val varchar(12))
insert into #LookUp values (1,'A'),(1,'D'),(1,'X'),(2,'B'),(2,'F');
WITH A AS
(
SELECT DISTINCT id
FROM #LookUp
)
SELECT
A.id,
STUFF
(
(
SELECT ',' + val
FROM #LookUp B
WHERE B.id = A.id
FOR XML PATH('')
),
1, 1, ''
) AS val
FROM A

Answer 4

Declare #LookUp table (id int,val varchar(12))
insert into #LookUp values (1,'A'),(1,'D'),(1,'X'),(2,'B'),(2,'F')
SELECT DISTINCT a.id, stuff((select '|' + val
from #LookUp c
where c.id = a.id
for xml path('')),1,1,'') as vall
FROM #LookUp a

Answer 5

I'll add a solution based on a recursive common table expression. With small modifications it should work in DB2 too (you have to change the row_number() function to rownumber() and how the concatenation works in the second list (use || instead of the concat function).
DECLARE #LookUp TABLE (id int, val varchar(12))
INSERT INTO #LookUp VALUES (1,'A'),(1,'D'),(1,'X'),(2,'B'),(2,'F')
;WITH
list1(rn, id, val) AS
(
SELECT row_number() OVER (PARTITION BY id ORDER BY id), id, val
FROM #LookUp
),
list2 (id, val, idx) AS
(
SELECT id, val, 1
FROM list1
WHERE rn = 1
UNION ALL
SELECT
list2.id,
CAST(CONCAT(list2.val, ' | ', list1.val) AS varchar(12)),
list2.idx + 1
FROM list2
JOIN list1 ON list2.id = list1.id
WHERE list2.idx + 1 = list1.rn
)
SELECT l2.id, l2.val
FROM list2 l2
JOIN (SELECT id, MAX(rn) maxid FROM list1 GROUP BY id) a
ON l2.id = a.id AND l2.idx = a.maxid
ORDER BY l2.id
This outputs:
id val
1 A | D | X
2 B | F