Querying a column that shows [count] of [max count] - sql

Question

I have 3 tables:
CustomerTypes table
Customers table (has a foreign key CustomerType). A customer can only have one customer type.
CustomersCollection table (contains many customerIds)
The primary SELECT of the query will be on CustomerTypes. I will be selecting two columns: CustomerTypeName and CountInCollection
The CustomerCount column in my query needs to show something like the following:
[Total # of Customers in CustomerType that are in Customer Collection] Of [Total # of Customers in CustomerType]
How can I get the proper customer count of the CustomerType that is part of the collection?
Example:
Customer1, Customer2, and Customer3 are all of CustomerTypeA.
CustomerCollection1 has customers Customer1 and Customer2 in it. The CountInCollection column for the CustomerTypeA record should show '2 of 3'.
Here is how I am able to get each count in separate queries:
-- Total customers in customer collection of customer type
SELECT COUNT(c.Id)
FROM Customer c
INNER JOIN CustomerCollection cc ON c.Id = cc.CustomerId
WHERE cc.CollectionId = 1019 AND c.CustomerTypeId=1000
-- Total customers in customer type
SELECT COUNT(Id) FROM
Customer WHERE CustomerTypeId=1000

Answer 1

Since you are using SQL 2008, I would take advantage of Common Table Expressions, aka CTEs, to assemble the data.
First, we'll need some test data. NOTE: I've thrown in some 'outliers' so that you can see where this kind of logic can bite you later.
DECLARE #CustomerTypes TABLE
(
CustomerTypeID INT,
[Customer Type] VARCHAR(100)
)
INSERT INTO #CustomerTypes
SELECT 1, 'TypeA'
UNION SELECT 2, 'TypeB'
UNION SELECT 3, 'TypeC' --NOTE: An outlier (not in customers-collection)
UNION SELECT 4, 'TypeD' --NOTE: An outlier (not in customers)
DECLARE #Customers TABLE
(
CustomerID INT,
CustomerTypeID INT
)
INSERT INTO #Customers
SELECT 1, 1
UNION SELECT 2, 1
UNION SELECT 3, 1
UNION SELECT 4, 2
UNION SELECT 5, 2
UNION SELECT 6, 2
UNION SELECT 7, 3
DECLARE #CustomersCollection TABLE
(
CollectionID INT IDENTITY(1,1),
CustomerID INT
)
INSERT INTO #CustomersCollection
(CustomerID)
SELECT TOP 2 --INSERT 2 of 3
CustomerID FROM #Customers WHERE CustomerTypeID = 1 --TypeA
INSERT INTO #CustomersCollection
(CustomerID)
SELECT TOP 1 --INSERT 1 of 3
CustomerID FROM #Customers WHERE CustomerTypeID = 2 --TypeB
Second, assemble the CTE data, and generate your output
;WITH CTE_COUNT_TYPE(CustomerTypeID, TypeCount)
AS
(
SELECT CustomerTypeID, COUNT(1)
FROM #Customers
GROUP BY CustomerTypeID
)
--SELECT * FROM CTE_COUNT_TYPE --DEBUG
,
CTE_COUNT_COLLECTION(CustomerTypeID, CollectionCount)
AS
(
SELECT CustomerTypeID, COUNT(1)
FROM #CustomersCollection CC
INNER JOIN #Customers C
ON CC.CustomerID = C.CustomerID
GROUP BY CustomerTypeID
)
--SELECT * FROM CTE_COUNT_COLLECTION --DEBUG
SELECT [Customer Type],
--CONVERT is necessary to combine INT data type (i.e. Count) and VARCHAR data type (i.e. 'as')
CONVERT(VARCHAR(100), COALESCE(CCC.CollectionCount, 0)) +
' of ' +
CONVERT(VARCHAR(100), COALESCE(CCT.TypeCount, 0)) As [Count in Collection]
FROM #CustomerTypes CT
LEFT OUTER JOIN #Customers C --Left outer join assists in outliers
ON CT.CustomerTypeID = C.CustomerTypeID
LEFT OUTER JOIN CTE_COUNT_TYPE CCT --Left outer join assists in outliers
ON CCT.CustomerTypeID = CT.CustomerTypeID
LEFT OUTER JOIN CTE_COUNT_COLLECTION CCC --Left outer join assists in outliers
ON CCC.CustomerTypeID = CT.CustomerTypeID
GROUP BY CT.[Customer Type]
, CCC.CollectionCount
, CCT.TypeCount

Answer 2

Hope so i get the question-
select
ct.CustomerTypeName as [Customer Type],
convert(varchar(30),count(cc.CollectionId)) + ' of ' + convert(varchar(30), count(c.CustomerId)) as [Count in Collection]
from
#Customer c
inner join #CustomerType ct on ct.CustomerTypeId = c.CustomerTypeId
left join #CustomerCollection cc on cc.CustomerId = c.CustomerId
group by
CustomerTypeName
Data script-
declare #customerType table (CustomerTypeId int, CustomerTypeName varchar(100))
insert into #customerType (CustomerTypeId, CustomerTypeName)
select 30, 'TypeA'
union
select 40, 'TypeB'
declare #customer table (CustomerId int, CustomerTypeId int)
insert into #customer (CustomerId, CustomerTypeId)
select 1, 30
union
select 2, 30
union
select 3, 30
union
select 4, 40
union
select 5, 40
union
select 6, 40
declare #customercollection table (CollectionId int, CustomerId int)
insert into #customercollection (CollectionId, CustomerId)
select 100, 1
union
select 200, 2
union
select 300, 5