Question

I’m getting duplicate account numbers when I user an inner join with transaction table. How do limit it so I do not see duplicate account numbers.

SELECT     A01_AccountMaster.AccountNumber, A01_AccountMaster.FamilyMemberType,
           A01_AccountMaster.AccountType, A01_AccountMaster.FamilyId, 
           A01_AccountMaster.Title, A01_AccountMaster.FirstName, 
           A01_AccountMaster.MiddleName, A01_AccountMaster.LastName,
           A01_AccountMaster.Suffix, A01_AccountMaster.OrganizationName,
           A01_AccountMaster.Status,
           T01_TransactionMaster.Date,
           T01_TransactionMaster.AccountNumber AS T01_Accountnumber  
FROM       A01_AccountMaster
INNER JOIN T01_TransactionMaster
      ON A01_AccountMaster.AccountNumber = T01_TransactionMaster.AccountNumber
WHERE      (A01_AccountMaster.Title = 'The')
           AND (T01_TransactionMaster.Date between '01/01/2010' and '09/12/2012')
ORDER BY   AccountNumber;

Answer 1

My suggestion would be to summarize the transaction table to get what you want from it.

To aggregate the data, use a query such as this:

select am.*, tm.NumTransactions
from A01_AccountMaster am join
     (select AccountNumber, count(*) as numtransactions
      from T01_TransactionMaster
      group by AccountNumber
     ) tm
     on am.AccountNumber = tm.AccountNumber
where . . .

Doing the aggregation at the subquery level simplifies the overall query, since you don’t have to do a group by with lots of fields. Also, if you introduce more tables, aggregating at the subquery level can prevent problems caused by interactions between the records in the other tables.