Get the mentioned output by SQL query - sql

Question

I appeared for an interview lately. The interviewer asked me the problem.
I have 2 tables:
First table is Location like this:
ID | City
---+-----------
1 | Mumbai
2 | Delhi
3 | Bangalore
Second table is Item like this:
Item | Location_id
-----+-------------
A | 1,2
B | 2,3
C | 1,2,3
Now we want the output as below
Item | Location
-----+-------------------------
A | Mumbai,Delhi
B | Delhi,Bangalore
C | Mumbai,Delhi,Bangalore
Please help me write the query.

Answer 1

You can use below query . String split works on SQL server 2016 and later versions.
Select * into #temp
from #location l
join (
select item,value from #item
CROSS APPLY STRING_SPLIT(location_id, ',')
) A on l.id=a.value
select
item,
stuff((
select ',' + u.city
from #temp u
where u.item = A.item
for xml path('')
),1,1,'') as List
from #temp A
group
by item
Drop table #temp

Answer 2

You want to STUFF all matching results into one column:
SELECT i.item,
STUFF((SELECT ',' + l.city
FROM location l
WHERE CHARINDEX(cast(l.id AS VARCHAR(4)),i.location_id)>0
FOR XML PATH ('')), 1, 1, '')
AS Location
FROM item i;
CHARINDEX finds the first instance of a substring in a string, in this case it finds that you have the number 1 for Mumbai, 2 for Dehli etc in your string of location_id.
STUFF combines your results into a single result.
SQLFiddle
UPDATE -
As pointed out by Rajneesh, this only works because your IDs are single digit. String splitting is probably the best way to handle the possibility of such IDs. That can still be done within this one query, without the need for a temp table.
SELECT i.item,
STUFF((SELECT ',' + l.city
FROM location l
WHERE l.id IN (select value from STRING_SPLIT(i.location_id, ','))
FOR XML PATH ('')), 1, 1, '')
AS Location
FROM item i;
SQLFiddle