Multiple joins, show one value if it occurs more than once - sql

Question

Say I have 3 tables below:
Table1 t1
id c1 c2
1 Jon Doe
2 James SMith
3 jolly rancher
Table2 t2
id c1
1 addr_1
1 addr_2
2 addr_1
2 addr_2
3 addr_1
Table3 t3
id c1
1 phone_1
2 phone_1
3 phone_1
3 phone_2
What i am trying to get is this:
1 Jon Doe addr_1 phone_1
1 addr_2
2 James SMith addr_1 phone_1
2 addr_2
3 jolly rancher addr_1 phone_1
3 phone_2
So that id is there for each output but other fields only once per that grouping—is this possible?

Answer 1

Is it possible? Yes. Is it ideal? Not really. I have to agree with D Stanley that it is definitely better to handle something like this in the app/reporting layer if you can.
However, if you really wanted to do this in SQL, you can see my solution below or go to the SQL fiddle here. This solution is not ideal because it's only working off the sample data you provided. If you have data where there are at least 2 phone numbers and at least 2 addresses for a given person, then the SQL below would need to be modified to handle that scenario. I've renamed the tables and columns to something a little more meaningful so that it's easier to read.
create table person(
id int,
firstName varchar(20),
lastName varchar(20)
)
create table address(
id int,
addr varchar(20)
)
create table phonenumber(
id int,
phoneNum varchar(20)
)
insert person (id, firstName, lastName)select 1, 'jon', 'doe'
insert person (id, firstName, lastName)select 2, 'james', 'smith'
insert person (id, firstName, lastName)select 3, 'jolly', 'rancher'
insert address(id, addr)select 1, 'addr_1'
insert address(id, addr)select 1, 'addr_2'
insert address(id, addr)select 2, 'addr_1'
insert address(id, addr)select 2, 'addr_2'
insert address(id, addr)select 3, 'addr_1'
insert phonenumber(id, phoneNum)select 1, 'phone_1'
insert phonenumber(id, phoneNum)select 2, 'phone_1'
insert phonenumber(id, phoneNum)select 3, 'phone_1'
insert phonenumber(id, phoneNum)select 3, 'phone_2'
CREATE TABLE #results(
id int,
firstName varchar(20),
lastName varchar(20),
address varchar(20),
phoneNumber varchar(20)
)
CREATE TABLE #finalresults(
id int,
firstName varchar(20),
lastName varchar(20),
address varchar(20),
phoneNumber varchar(20)
)
INSERT #results
(
id, firstName, lastName, address, phoneNumber
)
SELECT Person.id, Person.firstName, Person.lastName, address.addr, phonenumber.phoneNum
FROM Person
INNER JOIN address
ON person.id = address.id
INNER JOIN phonenumber
ON person.id = phonenumber.id
DECLARE #id int, #firstname varchar(20), #lastname varchar(20),
#address varchar(20), #phonenumber varchar(20)
DECLARE my_cursor CURSOR
FOR SELECT * FROM #results
OPEN my_cursor
FETCH NEXT FROM my_cursor INTO #id, #firstname, #lastname, #address, #phonenumber
while ##fetch_status = 0
BEGIN
IF NOT EXISTS (SELECT 1 FROM #finalresults WHERE id = #id)
BEGIN
INSERT #finalresults(id, firstname, lastname, address, phonenumber)
SELECT #id, #firstname, #lastname, #address, #phonenumber
END
ELSE
BEGIN
INSERT #finalresults(id, firstname, lastname, address, phonenumber)
SELECT distinct #id, '', '',
CASE WHEN finalAddress.address IS NOT NULL
THEN ''
ELSE #address
END,
CASE WHEN finalPhoneNumber.phonenumber IS NOT NULL
THEN ''
ELSE #phonenumber
END
FROM #finalresults
LEFT OUTER JOIN #finalresults finalAddress
ON finalAddress.id = #id
AND finalAddress.address = #address
LEFT OUTER JOIN #finalresults finalPhoneNumber
ON finalPhoneNumber.id = #id
AND finalPhoneNumber.phonenumber = #phonenumber
END
FETCH NEXT FROM my_cursor INTO #id, #firstname, #lastname, #address, #phonenumber
END
CLOSE my_cursor
DEALLOCATE my_cursor
SELECT * FROM #finalresults