SQL: Merging rows with comma separated values in columns - sql

Question

We have a table like this:
Group | User | Team
-------------------
Grp1 | U1 | T1,T2
Grp1 | U2 | T1,T2,T3
Grp1 | U3 | T4
Grp2 | U4 | T2,T4
Grp2 | U5 | T5
I want to create a view which has the data like this:
Group | Teams
-------------
Grp1 | T1,T2,T3,T4
Grp2 | T2,T4,T5
Can somebody please help me? I tried doing few trail and errors and finally I am at a state where I am not even sure where to start from now

Answer 1

Here is my approach.
I am using cursor but you can do it in while loop also.
The only issue is that teams in new table are not distinct but I think you can play with string commands and it will sort the issue.
CREATE TABLE #tbl1 ([GROUP] varchar(20), [USER] VARCHAR(20), team VARCHAR(20))
INSERT INTO #tbl1 ( [GROUP], [USER],team )
VALUES ( 'Grp1', 'U1', 'T1,T2'), ( 'Grp1', 'U2', 'T3,T4'), ( 'Grp1', 'U3', 'T4'),
( 'Grp2', 'U1', 'T1,T2'), ( 'Grp2', 'U2', 'T3,T4')
CREATE TABLE #tbl2 ([GROUP] varchar(20), team VARCHAR(20))
DECLARE #ListOfteams VARCHAR(max)
DECLARE #grp VARCHAR(20)
DECLARE Curs CURSOR FAST_FORWARD
FOR
SELECT DISTINCT [GROUP]
FROM #tbl1 AS T
OPEN Curs
FETCH NEXT FROM Curs INTO #grp
WHILE ##FETCH_STATUS = 0
BEGIN
SET #ListOfteams= ''
SELECT #ListOfteams= #ListOfteams+ [Team] + ',' FROM #tbl1 AS CL WHERE CL.[GROUP] = #grp ORDER BY [CL].[USER]
INSERT INTO #tbl2 ( [GROUP],team )
SELECT DISTINCT #grp,
SUBSTRING(#ListOfteams, 1, LEN(#ListOfteams)-1)
FROM #tbl1 AS T
WHERE T.[GROUP] = #grp;
FETCH NEXT FROM Curs INTO #grp
END
CLOSE Curs
DEALLOCATE Curs;
SELECT *
FROM #tbl2 AS T
Here is ow it works: http://rextester.com/BYK57259
+-------+----------------+
| GROUP | team |
+-------+----------------+
| Grp1 | T1,T2,T3,T4,T4 |
| Grp2 | T1,T2,T3,T4 |
+-------+----------------+

Answer 2

Here is how am doing this, first convert the comma seperated team names to individual rows based on their groups and then take the unique team grp and team names. Now apply the listagg function for the unique team names to achieve the result.
with t as
(
select 'Grp1' grp,'U1' user1,'T1,T2' team from dual
union all
select 'Grp1','U2','T1,T2,T3' from dual
union all
select 'Grp1','U3','T4' from dual
union all
select 'Grp2','U4','T2,T4' from dual
union all
select 'Grp2','U5','T5' from dual
),
g as
(
select distinct grp, regexp_substr(team,'[^,]+',1,level) team1
from t
connect by level <= LENGTH(REGEXP_REPLACE(team, '[^,]+')) + 1
--group by grp
)
select grp,listagg(team1,',') within group (order by team1) from g
group by grp;
THis is the output I got
+----+-------------------------------------------+
|GRP ||Teams
+----+-------------------------------------------+
|Grp1|T1,T2,T3,T4 |
|Grp2|T2,T4,T5 |
+----+-------------------------------------------+