Transforming a column in rows [duplicate] - sql

Question

I have the following dataset
Account Contact
1 324324324
1 674323234
2 833343432
2 433243443
3 787655455
4 754327545
4 455435435
5 543544355
5 432455553
5 432433242
5 432432432
I'd like output as follows:
Account Contact1 Contact2 Contact3 Contact4
1 324324324 674323234
2 833343432 433243443
3 787655455
4 754327545 455435435
5 543544355 432455553 432433242 432432432
The problem is also that I have an unfixed amount of Accounts & unfixed amount of Contacts

Answer 1

If you are going to apply the PIVOT function, you will need to use an aggregate function to get the result but you will also want to use a windowing function like row_number() to generate a unique sequence for each contact in the account.
First, you will query your data similar to:
select account, contact,
'contact'
+ cast(row_number() over(partition by account
order by contact) as varchar(10)) seq
from yourtable
See SQL Fiddle with Demo. This will create a new column with the unique sequence:
| ACCOUNT | CONTACT | SEQ |
|---------|-----------|----------|
| 1 | 324324324 | contact1 |
| 1 | 674323234 | contact2 |
If you have a limited number of columns, then you could hard-code your query:
select account,
contact1, contact2, contact3, contact4
from
(
select account, contact,
'contact'
+ cast(row_number() over(partition by account
order by contact) as varchar(10)) seq
from yourtable
) d
pivot
(
max(contact)
for seq in (contact1, contact2, contact3, contact4)
) piv;
See SQL Fiddle with Demo
If you have an unknown number of columns, then you will have to use dynamic SQL:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX)
select #cols = STUFF((SELECT ',' + QUOTENAME(seq)
from
(
select 'contact'
+ cast(row_number() over(partition by account
order by contact) as varchar(10)) seq
from yourtable
) d
group by seq
order by seq
FOR XML PATH(''), TYPE
).value('.', 'NVARCHAR(MAX)')
,1,1,'')
set #query = 'SELECT account, ' + #cols + '
from
(
select account, contact,
''contact''
+ cast(row_number() over(partition by account
order by contact) as varchar(10)) seq
from yourtable
) x
pivot
(
max(contact)
for seq in (' + #cols + ')
) p '
execute sp_executesql #query;
See SQL Fiddle with Demo. Both will give you a result of:
| ACCOUNT | CONTACT1 | CONTACT2 | CONTACT3 | CONTACT4 |
|---------|-----------|-----------|-----------|-----------|
| 1 | 324324324 | 674323234 | (null) | (null) |
| 2 | 433243443 | 833343432 | (null) | (null) |
| 3 | 787655455 | (null) | (null) | (null) |
| 4 | 455435435 | 754327545 | (null) | (null) |
| 5 | 432432432 | 432433242 | 432455553 | 543544355 |

Answer 2

Just a slightly different way to generate the dynamic PIVOT:
DECLARE #c INT;
SELECT TOP 1 #c = COUNT(*)
FROM dbo.YourTable
GROUP BY Account
ORDER BY COUNT(*) DESC;
DECLARE #dc1 NVARCHAR(MAX) = N'', #dc2 NVARCHAR(MAX) = N'', #sql NVARCHAR(MAX);
SELECT #dc1 += ',Contact' + RTRIM(i), #dc2 += ',[Contact' + RTRIM(i) + ']'
FROM (SELECT TOP (#c) i = number + 1
FROM master.dbo.spt_values WHERE type = N'P' ORDER BY number) AS x;
SET #sql = N'SELECT Account ' + #dc1 +
' FROM (SELECT Account, Contact, rn = ''Contact''
+ RTRIM(ROW_NUMBER() OVER (PARTITION BY Account ORDER BY Contact))
FROM dbo.YourTable) AS src PIVOT (MAX(Contact) FOR rn IN ('
+ STUFF(#dc2, 1, 1, '') + ')) AS p;';
EXEC sp_executesql #sql;
SQLiddle demo