Using COUNT with MAX in SQL - sql

Question

I am trying to find which customer has the most transactions. Transaction table has an foreign key that identifies each transaction with a customer. What I currently is the following code:
WITH Customers as (
SELECT
[CustName] as 'Customer',
[TRANSACTION].[CustID] as 'Total # of Transactions'
FROM [dbo].[CUSTOMER]
INNER JOIN [dbo].[TRANSACTION]
ON [CUSTOMER].[CustID] = [TRANSACTION].[CustID]
)
SELECT *
FROM Customers
WHERE 'Total # of Transactions' = (SELECT MAX('Total # of Transactions') FROM Customers);
Two things are wrong:
1) The latter part of the code doesn't accept 'Total # of Transactions'. If I were to rename it to a single word, I could treat it kind of like a variable.
2) My last SELECT statement gives me a result of the customer and all their transactions, but doesn't give me a COUNT of those transactions. I'm not sure how to use COUNT in conjunction with MAX.

Answer 1

First select customers and transaction count.
Then select the largest one.
Them limit your select to that item.
Work you way from the inside out.
SELECT *
FROM Customers
WHERE CustID =
(
SELECT TOP 1 CustID
FROM (SELECT CustID, COUNT(*) AS TCOUNT
FROM TRANSACTIONS
GROUP BY CustID) T
ORDER BY T.TCOUNT DESC
) TT

Answer 2

This should get you everything you need. To get the top customer just add Top 1 to the select
WITH Customers as (
SELECT
[CustName] as Name
FROM [dbo].[CUSTOMER]
INNER JOIN [dbo].[TRANSACTION]
ON [CUSTOMER].[CustID] = [TRANSACTION].[CustID]
)
-- to get count of transactions
Select Count(*) as count, Name
FROM Customers
Group by Name
Order By Count(*) desc

Answer 3

Your inner table just returns CustID as a total number of transactions? You need to start by finding the total count for each customer. Also for a column you can use [Name], when you use apostrophes it thinks you are comparing a string. If you want to return all customers with the highest count, you could use this:
WITH TransactionCounts as (
SELECT
CustID,
COUNT(*) AS TransactionCount
FROM [dbo].[TRANSACTION]
GROUP BY CustID
)
SELECT TOP 1 CUSTOMER.*, TransactionCount
FROM TransactionCounts
INNER JOIN CUSTOMER ON CUSTOMER.CustID = TransactionCounts.CustId
ORDER BY TransactionCount DESC
-- alternate to select all if multiple customers are tied for highest count
--WHERE TransactionCount = (SELECT MAX(TransactionCount) FROM TransactionCounts)