SQL query select record with Max - sql

Question

I have these records below :
CustomerID | Name | Store | Quantity
1 | Elie | HO | 16
1 | Elie | S1 | 4
I would like to filter customers by taking only their max quantity?
I tried it with Max, but the problem I cannot render all the fields with it. If I add main.store in the first line, the second row shows.
Is there any solution?
Select main.CUSTOMER_ID, main.Name
from
(
Select Name = cus.FIRST_NAME + ' ' + cus.LAST_NAME,
Store = cs.NAME
,Transaction_Number = count(ts.TRANSACTION_SUMMARY_ID)
,cus.CUSTOMER_ID
from TRANSACTION_SUMMARY ts
inner join dbo.CUSTOMER cus
on ts.CUSTOMER_ID = cus.CUSTOMER_ID
inner join dbo.CORPORATE_STORE cs
on ts.CORPORATE_STORE_ID = cs.CORPORATE_STORE_ID
Group by cus.CUSTOMER_ID
,cus.FIRST_NAME
,cus.LAST_NAME
,cs.Name
) as main
Group by CUSTOMER_ID
,main.Name
order by main.CUSTOMER_ID

Answer 1

This is a good use of window functions:
with t as (
Select Name = cus.FIRST_NAME + ' ' + cus.LAST_NAME,
Store = cs.NAME,
Transaction_Number = count(ts.TRANSACTION_SUMMARY_ID) , cus.CUSTOMER_ID
from TRANSACTION_SUMMARY ts
inner join dbo.CUSTOMER cus on ts.CUSTOMER_ID = cus.CUSTOMER_ID
inner join dbo.CORPORATE_STORE cs on ts.CORPORATE_STORE_ID = cs.CORPORATE_STORE_ID
Group by cus.CUSTOMER_ID, cus.FIRST_NAME, cus.LAST_NAME, cs.Name
)
select name, store, Transaction_Number, CUSTOMER_ID
from (select t.*,
row_number() over (partition by customer_id order by transaction_number desc) as seqnum
from t
) t
where seqnum = 1;
You can actually dispense with the subquery. However, using window functions with aggregations looks funny at first:
with t as (
Select Name = cus.FIRST_NAME + ' ' + cus.LAST_NAME,
Store = cs.NAME,
Transaction_Number = count(ts.TRANSACTION_SUMMARY_ID) , cus.CUSTOMER_ID,
row_number() over (partition by cus.CUSTOMER_ID
order by count(ts.TRANSACTION_SUMMARY_ID) desc
) as seqnum
from TRANSACTION_SUMMARY ts
inner join dbo.CUSTOMER cus on ts.CUSTOMER_ID = cus.CUSTOMER_ID
inner join dbo.CORPORATE_STORE cs on ts.CORPORATE_STORE_ID = cs.CORPORATE_STORE_ID
Group by cus.CUSTOMER_ID, cus.FIRST_NAME, cus.LAST_NAME, cs.Name
)
select name, store, Transaction_Number, CUSTOMER_ID
from t
where seqnum = 1;

Answer 2

Please try:
select * From tbl a
where a.Quantity=
(select MAX(b.Quantity) from tbl b where a.CustomerID=b.CustomerID)

Answer 3

what you want is
select customer_id, max( quantity )
from main
group by customer_id
then you can use this to join to itself if you want
select *
from main
, (
select customer_id, max( quantity ) qty
from main
group by customer_id
) m
where main.customer_id = m.customer_id
and main.quantity = m.qty

Answer 4

Obviously, name has no business being in this table, but you included it, so I did too...
SELECT x.*
FROM my_table x
JOIN
( SELECT customerid
, name
, MAX(quantity) max_quantity
FROM my_table
GROUP
BY customerid
, name
) y
ON y.customerid = x.customerid
AND y.name = x.name
AND y.max_quantity = x.quantity;