SQL query like GROUP BY with OR condition - sql-server

Question

I'll try to describe the real situation. In our company we have a reservation system with a table, let's call it Customers, where e-mail and phone contacts are saved with each incoming order - that's the part of a system I can't change. I'm facing the problem how to get count of unique customers. With the unique customer I mean group of people who has either the same e-mail or same phone number.
Example 1: From the real life you can imagine Tom and Sandra who are married. Tom, who ordered 4 products, filled in our reservation system 3 different e-mail addresses and 2 different phone numbers when one of them shares with Sandra (as a homephone) so I can presume they are connected somehow. Sandra except this shared phone number filled also her private one and for both orders she used only one e-mail address. For me this means to count all of the following rows as one unique customer. So in fact this unique customer may grow up into the whole family.
ID E-mail Phone Comment
---- ------------------- -------------- ------------------------------
0 tom#email.com [phone] First row
1 tommy#email.com [phone] Same phone, different e-mail
2 thomas#email.com [phone] Same phone, different e-mail
3 thomas#email.com [phone] Same e-mail, different phone
4 sandra#email.com [phone] Same phone, different e-mail
5 sandra#email.com [phone] Same e-mail, different phone
As ypercube said I will probably need a recursion to count all of these unique customers.
Example 2: Here is the example of what I want to do.Is it possible to get count of unique customers without using recursion for instance by using cursor or something or is the recursion necessary ?
ID E-mail Phone Comment
---- ------------------- -------------- ------------------------------
0 linsey#email.com [phone] ─┐
1 louise#email.com [phone] ├─ 1. unique customer
2 louise#email.com [phone] ─┘
---- ------------------- -------------- ------------------------------
3 steven#email.com [phone] ─┐
4 steven#email.com [phone] ├─ 2. unique customer
5 sandra#email.com [phone] ─┘
---- ------------------- -------------- ------------------------------
6 george#email.com [phone] ─── 3. unique customer
---- ------------------- -------------- ------------------------------
7 xavier#email.com [phone] ─┐
8 xavier#email.com [phone] ├─ 4. unique customer
9 xavier#email.com [phone] ─┘
---- ------------------- -------------- ------------------------------
10 robert#email.com [phone] ─┐
11 miriam#email.com [phone] ├─ 5. unique customer
12 sherry#email.com [phone] ─┘
---- ------------------- -------------- ------------------------------
----------------------------------------------------------------------
Result ∑ = 5 unique customers
----------------------------------------------------------------------
I've tried a query with GROUP BY but I don't know how to group the result by either first or second column. I'm looking for let's say something like
SELECT COUNT(*) FROM Customers
GROUP BY Email OR Phone
Thanks again for any suggestions
P.S.
I really appreciate the answers for this question before the complete rephrase. Now the answers here may not correspond to the update so please don't downvote here if you're going to do it (except the question of course :). I completely rewrote this post.Thanks and sorry for my wrong start.

Answer 1

Here is a full solution using a recursive CTE.
;WITH Nodes AS
(
SELECT DENSE_RANK() OVER (ORDER BY Part, PartRank) SetId
, [ID]
FROM
(
SELECT [ID], 1 Part, DENSE_RANK() OVER (ORDER BY [E-mail]) PartRank
FROM dbo.Customer
UNION ALL
SELECT [ID], 2, DENSE_RANK() OVER (ORDER BY Phone) PartRank
FROM dbo.Customer
) A
),
Links AS
(
SELECT DISTINCT A.Id, B.Id LinkedId
FROM Nodes A
JOIN Nodes B ON B.SetId = A.SetId AND B.Id < A.Id
),
Routes AS
(
SELECT DISTINCT Id, Id LinkedId
FROM dbo.Customer
UNION ALL
SELECT DISTINCT Id, LinkedId
FROM Links
UNION ALL
SELECT A.Id, B.LinkedId
FROM Links A
JOIN Routes B ON B.Id = A.LinkedId AND B.LinkedId < A.Id
),
TransitiveClosure AS
(
SELECT Id, Id LinkedId
FROM Links
UNION
SELECT LinkedId Id, LinkedId
FROM Links
UNION
SELECT Id, LinkedId
FROM Routes
),
UniqueCustomers AS
(
SELECT Id, MIN(LinkedId) UniqueCustomerId
FROM TransitiveClosure
GROUP BY Id
)
SELECT A.Id, A.[E-mail], A.Phone, B.UniqueCustomerId
FROM dbo.Customer A
JOIN UniqueCustomers B ON B.Id = A.Id

Answer 2

Finding groups that have only same Phone:
SELECT
ID
, Name
, Phone
, DENSE_RANK() OVER (ORDER BY Phone) AS GroupPhone
FROM
MyTable
ORDER BY
GroupPhone
, ID
Finding groups that have only same Name:
SELECT
ID
, Name
, Phone
, DENSE_RANK() OVER (ORDER BY Name) AS GroupName
FROM
MyTable
ORDER BY
GroupName
, ID
Now, for the (complex) query you describe, let's say we have a table like this instead:
ID Name Phone
---- ------------- -------------
0 Kate [phone]
1 Sandra [phone]
2 Thomas [phone]
3 Robert [phone]
4 Thomas [phone]
5 George [phone]
6 Kate [phone]
7 Robert [phone]
--------------------------------
Should all these be in one group? As they all share name or phone with someone else, forming a "chain" of relative persons:
0-6 same name
6-1-3 same phone
3-7 same name
7-4 same-phone
4-2 same name
2-5 bame phone

Answer 3

For the dataset in the example you could write something like this:
;WITH Temp AS (
SELECT Name, Phone,
DENSE_RANK() OVER (ORDER BY Name) AS NameGroup,
DENSE_RANK() OVER (ORDER BY Phone) AS PhoneGroup
FROM MyTable)
SELECT MAX(Phone), MAX(Name), COUNT(*)
FROM Temp
GROUP BY NameGroup, PhoneGroup

Answer 4

I don't know if this is the best solution, but here it is:
SELECT
MyTable.ID, MyTable.Name, MyTable.Phone,
CASE WHEN N.No = 1 AND P.No = 1 THEN 1
WHEN N.No = 1 AND P.No > 1 THEN 2
WHEN N.No > 1 OR P.No > 1 THEN 3
END as GroupRes
FROM
MyTable
JOIN (SELECT Name, count(Name) No FROM MyTable GROUP BY Name) N on MyTable.Name = N.Name
JOIN (SELECT Phone, count(Phone) No FROM MyTable GROUP BY Phone) P on MyTable.Phone = P.Phone
The problem is that here are some joins made on varchars and could end up in increasing execution time.

Answer 5

Here is my solution:
SELECT p.LastName, P.FirstName, P.HomePhone,
CASE
WHEN ph.PhoneCount=1 THEN
CASE
WHEN n.NameCount=1 THEN 'unique name and phone'
ELSE 'common name'
END
ELSE
CASE
WHEN n.NameCount=1 THEN 'common phone'
ELSE 'common phone and name'
END
END
FROM Contacts p
INNER JOIN
(SELECT HomePhone, count(LastName) as PhoneCount
FROM Contacts
GROUP BY HomePhone) ph ON ph.HomePhone = p.HomePhone
INNER JOIN
(SELECT FirstName, count(LastName) as NameCount
FROM Contacts
GROUP BY FirstName) n ON n.FirstName = p.FirstName
LastN FirstN Phone Comment
Hoover Brenda 8138282334 unique name and phone
Washington Brian 9044563211 common name
Roosevelt Brian 7737653279 common name
Reagan Charles 7734567869 unique name and phone