SELECT From Multiple tables with many to many relations - sql

Question

Hello everyone I have inherirted a poorly designed database and I need to get some information from 3 tables
Franchise
Id(Int, PK)
FrID (varchar(50))
FirstName (varchar(50))
LastName (varchar(50))
Store
Id (Int, PK)
FrID (varchar(50))
StoreNumber (varchar(50))
StoreName
Address
Pricing
Id (int, PK)
StoreNumber (varchar(50))
Price1
Price2
Price3
and the data
ID, FrID ,FirstName,LastName
1, 10 ,John Q , TestCase
2, 10 ,Jack Q , TestCase
3, 11 ,Jack Q , TestCase
ID, FrID, StoreNumber , StoreName , Address
10, 10 , 22222 , TestStore1, 123 Main street
11, 10 , 33333 , TestStore2, 144 Last Street
12, 10 , 44444 , TestStore2, 145 Next Street
13, 11 , 55555 , Other Test, 156 Other st
ID, StoreNumber, Price1, Price2, Price3
1, 22222 , 19.99, 20.99 , 30.99
2, 33333 , 19.99, 20.99 , 30.99
3, 44444 , 19.99, 20.99 , 30.99
4, 55555 , 19.99, 20.99 , 30.99
Here is what I have done
SELECT F.FirstName,F.LastName,F.FrID , S.StoreNumber,S.StoreName,S.Address,
P.Price1,P.Price2,P.Price3
FROM Franchisee F
JOIN Store S on F.FrID = S.FrID
JOIN Pricing P on P.StoreNumber = S.StoreNumber
This part works, but I end up with lots of duplicates, For example Jack Q gets listed for his store plus every store that John Q is on. Is there anyway to fix this with out a database redesign.

Answer 1

Okay, there is a whole laundry list of issues such as character fields such as [FrId] being used as strings, reserved words such as [address] being used as name, etc.
Let's put the bad design issues aside.
First, I need to create a quick test environment. I did not put in Foreign Keys since that constraint is not needed to get the correct answer.
--
-- Setup test tables
--
-- Just playing
use Tempdb;
go
-- drop table
if object_id('franchise')> 0
drop table franchise;
go
-- create table
create table franchise
(
Id int primary key,
FrID varchar(50),
FirstName varchar(50),
LastName varchar(50)
);
-- insert data
insert into franchise values
( 1, 10, 'John Q', 'TestCase'),
( 2, 10, 'Jack Q', 'TestCase'),
( 3, 11, 'Jack Q', 'TestCase');
-- select data
select * from franchise;
go
-- drop table
if object_id('store')> 0
drop table store;
go
-- create table
create table store
(
Id int primary key,
FrID varchar(50),
StoreNumber varchar(50),
StoreName varchar(50),
Address varchar(50)
);
-- insert data
insert into store values
(10, 10, 22222, 'TestStore1', '123 Main street'),
(11, 10, 33333, 'TestStore2', '144 Last Street'),
(12, 10, 44444, 'TestStore2', '145 Next Street'),
(13, 11, 55555, 'Other Test', '156 Other Street');
-- select data
select * from store;
go
-- drop table
if object_id('pricing')> 0
drop table pricing;
go
-- create table
create table pricing
(
Id int primary key,
StoreNumber varchar(50),
Price1 money,
Price2 money,
Price3 money
);
-- insert data
insert into pricing values
(1, 22222, 19.99, 20.99 , 30.99),
(2, 33333, 19.99, 20.99 , 30.99),
(3, 44444, 19.99, 20.99 , 30.99),
(4, 55555, 19.95, 20.95 , 30.95);
-- select data
select * from pricing;
go
The main issue is that the franchise table should have the primary key (PK) on FrId, not Id. I do not understand why there are duplicates.
However, the query below removes them by grouping. I changed the pricing data for Jack Q to show it is a different record.
--
-- Fixed Query - Version 1
--
select
f.FirstName,
f.LastName,
f.FrID,
s.StoreNumber,
s.StoreName,
s.Address,
p.Price1,
p.Price2,
p.Price3
from
-- Remove duplicates from francise
(
select
LastName,
FirstName,
Max(FrID) as FrID
from
franchise
group by
LastName,
FirstName
) as f
join store s on f.FrID = s.FrID
join pricing p on p.StoreNumber = s.StoreNumber;
The correct output is below.
If I am correct, remove the duplicates entries and change the primary key.
Change Requirements
Okay, you are placing two or more owners in the same table.
Below uses a sub query to combine the owners list into one string. Another way is to have a flag called primary owner. Choose that as the display name.
--
-- Fixed Query - Version 2
--
select
f.OwnersList,
f.FrID,
s.StoreNumber,
s.StoreName,
s.Address,
p.Price1,
p.Price2,
p.Price3
from
-- Compose owners list
(
select
FrID,
(
SELECT FirstName + ' ' + LastName + ';'
FROM franchise as inner1
WHERE inner1.FrID = outer1.FrID
FOR XML PATH('')
) as OwnersList
from franchise as outer1
group by FrID
) as f (FrId, OwnersList)
join store s on f.FrID = s.FrID
join pricing p on p.StoreNumber = s.StoreNumber
Here is the output from the second query.