SQL Select multiple joins and MAX(field) result - sql

Question

I'm using IBM Cognos to create a report which allows for fairly standard SQL. I am ultimately trying to take data from 2 tables and compare them to each other to ensure they match. Billing_Term, Bill_Period and Contract_Term_Amount all need to match when comparing a given Contract_Number, Contract_Item and Stream_Type between t1 and t3 but only for the MAX Seq_No from t3.
I tried a simple MAX() on Seq_No but that didn't work so I'm looking for help in limiting the results to the MAX Seq_No for the associated query results.
SELECT
t1.Contract_Number,
t1.Contract_Item,
t1.Stream_Type,
t1.Billing_Term,
t1.Bill_Period,
t1.Contract_Term_Amount,
t2.Reference_Document,
t3.Billing_Term,
t3.Bill_Period,
t3.Contract_Term_Amount,
t3.Seq_No
FROM
LeasingStreamData t1
INNER JOIN ContractsData t2 ON t1.Contract_Number = t2.Sales_Document
LEFT JOIN LeasingStreamData t3 ON t2.Reference_Document = t3.Contract_Number AND
t1.Contract_Item = t3.Contract_Item AND
t1.Stream_Type = t3.Stream_Type
WHERE
t1.Contract_Number IN ([some list of contracts])
GROUP BY
t1.Contract_Number,
t1.Contract_Item,
t1.Stream_Type,
t1.Billing_Term,
t1.Bill_Period,
t1.Contract_Term_Amount,
t2.Reference_Document,
t3.Billing_Term,
t3.Bill_Period,
t3.Contract_Term_Amount,
t3.Seq_No
I hope this is enough to get some much needed help, many thanks for any assistance you can provide!

Answer 1

If I understand you requirement, I think you want to create queries and join them in a way that will look like this SQL:
SELECT
t1.Contract_Number
, t1.Contract_Item
, t1.Stream_Type
, t1.Billing_Term
, t1.Bill_Period
, t1.Contract_Term_Amount
, t2.Reference_Document
, t3.Billing_Term
, t3.Bill_Period
, t3.Contract_Term_Amount
, t3.Seq_No
FROM (
SELECT Contract_Number
, Contract_Item
, Stream_Type
, Billing_Term
, Bill_Period
, Contract_Term_Amount
FROM LeasingStreamData
WHERE Contract_Number in ([some list of contracts])
) t1
INNER JOIN (
SELECT Sales_Document
, Reference_Document
FROM ContractsData
WHERE Sales_Document in ([some list of contracts])
) t2 ON t1.Contract_Number = t2.Sales_Document
INNER JOIN LeasingStreamData t3 ON t2.Reference_Document = t3.Contract_Number
AND t1.Contract_Item = t3.Contract_Item
AND t1.Stream_Type = t3.Stream_Type
INNER JOIN (
select max(Seq_No) as Seq_No
, Contract_Number
, Contract_Item
, Stream_Type
from LeasingStreamData lsd
group by Contract_Number
, Contract_Item
, Stream_Type
) maxseq on maxseq.Contract_Number = t3.Contract_Number
and maxseq.Contract Item = t3.Contract_Item
and maxseq.Stream_Type = t3.Stream_Type
and maxseq.Seq_No = t3.Seq_No
WHERE t1.Billing_Term <> t3.Billing_Term
and t1.Bill_Period <> t3.Bill_Period
and t1.Contract_Term_Amount <> t3.Contract_Term_Amount
GROUP BY
t1.Contract_Number
, t1.Contract_Item
, t1.Stream_Type
, t1.Billing_Term
, t1.Bill_Period
, t1.Contract_Term_Amount
, t2.Reference_Document
, t3.Billing_Term
, t3.Bill_Period
, t3.Contract_Term_Amount
, t3.Seq_No
I think this will filter to only the max Seq_No for t3 and return only the records that you care about (the ones that don't match).

Answer 2

Try this:
SELECT t1.Contract_Number
,t1.Contract_Item
,t1.Stream_Type
,t1.Billing_Term
,t1.Bill_Period
,t1.Contract_Term_Amount
,t2.Reference_Document
,t3.Billing_Term
,t3.Bill_Period
,t3.Contract_Term_Amount
,t3.Seq_No
FROM LeasingStreamData t1
INNER JOIN ContractsData t2 ON t1.Contract_Number = t2.Sales_Document
LEFT JOIN (
SELECT Contract_Number
,Contract_Item
,Stream_type
,MAX(Seq_No) AS "Seq_No"
FROM LeasingStreamData
GROUP BY Contract_Number
,Contract_Item
,Stream_Type
) t3 ON t2.Reference_Document = t3.Contract_Number
AND t1.Contract_Item = t3.Contract_Item
AND t1.Stream_Type = t3.Stream_Type
WHERE t1.Contract_Number IN ([some list of contracts])
Since the rollup for the aggregate function (MAX) relies on the group by to determine context, you have to isolate it via a subquery to get the max before joining to the rest of the tables.
Also, since you are preaggregating the max sequence number, you no longer need a group by in the main query.