Flattening out a normalized SQL Server 2008 R2 database - sql

Question

I am working with SQL Server 2008 R2.
I have 3 tables the data is normalized and I am looking to grab the 'Home' and 'Cell' phone for Bob Dole. However I need to only get the highest sequence phone number of each type. (below is an example of Bob Dole having 2 cell phones and the sequence number for each is 2 and 3 respectively)
Table PersonPhoneNumber
PersonPhoneNumberId Person PhoneNumberId PhoneNumberTypeId Sequence
Guid - vvv Bob Dole Guid - A 1 1
Guid - www Bob Dole Guid - B 2 2
Guid - xxx Bob Dole Guid - C 2 3
Table PhoneNumber
PhoneNumberId Number
Guid - A 111-111-1111
Guid - B 222-222-2222
Guid - C 333-333-3333
Table PhoneNumberType
PhoneNumberTypeId PhoneNumberType
1 Home
2 Cell
My desired output would be this (notice that I only returned the first Cell number.):
Person Home Cell
Bob Dole 111-111-1111 222-222-2222
I have been having issues flattening out the data
Any help with the query would be great!

Answer 1

You can use a row_number() and an aggregate function with CASE expression to convert the data from rows to columns:
select person,
max(case when rn = 1 and PhoneNumberType = 'Home' then number end) home,
max(case when rn = 1 and PhoneNumberType = 'Cell' then number end) cell
from
(
select ppn.person, pn.number,
pt.PhoneNumberType,
row_number() over(partition by ppn.person, ppn.PhoneNumberTypeId
order by ppn.sequence) rn
from PersonPhoneNumber ppn
inner join PhoneNumber pn
on ppn.PhoneNumberId = pn.PhoneNumberId
inner join PhoneNumberType pt
on ppn.PhoneNumberTypeId = pt.PhoneNumberTypeId
) d
group by person;
See SQL Fiddle with Demo
This could also be done using the PIVOT function:
select person,
home,
cell
from
(
select ppn.person, pn.number,
pt.PhoneNumberType,
row_number() over(partition by ppn.person, ppn.PhoneNumberTypeId
order by ppn.sequence) rn
from PersonPhoneNumber ppn
inner join PhoneNumber pn
on ppn.PhoneNumberId = pn.PhoneNumberId
inner join PhoneNumberType pt
on ppn.PhoneNumberTypeId = pt.PhoneNumberTypeId
) d
pivot
(
max(number)
for PhoneNumberType in (Home, Cell)
) piv
where rn = 1;
See SQL Fiddle with Demo

Answer 2

Here's an example with a sub-query to get the first sequence number for each Type. The outer query then uses a CASE statement to create the Home and Cell Columns.
SELECT P.Person
,MAX(CASE WHEN P.PhoneNumberTypeId = 1 THEN N.Number ELSE NULL END) AS Home
,MAX(CASE WHEN P.PhoneNumberTypeId = 2 THEN N.Number ELSE NULL END) AS Cell
FROM PersonPhoneNumber P
INNER JOIN
PhoneNumber N
ON P.PhoneNumberId = N.PhoneNumberId
INNER JOIN
(
SELECT Person
,PhoneNumberTypeId
,MIN(Sequence) AS FIRST_NUM
FROM PersonPhoneNumber
GROUP BY
Person
,PhoneNumberTypeId
) SQ1
ON P.Person = SQ1.Person
AND P.PhoneNumberTypeId = SQ1.PhoneNumberTypeId
AND P.Sequence = SQ1.FIRST_NUM
GROUP BY
P.PERSON