Hello, I have a SQL query that I'm currently solving by doing two queries. I am wondering if there is a way to do it in a single query that makes it more efficient.

Consider two tables:

Transaction_Entries table and Transactions, each one defined below:

Transactions
- id
- reference_number  (varchar)


Transaction_Entries
- id
- account_id
- transaction_id (references Transactions table)

Notes: There are multiple transaction entries per transaction. Some transactions are related, and will have the same reference_number string.

To get all transaction entries for Account X, then I would do

SELECT E.*, T.reference_number 
  FROM Transaction_Entries E 
  JOIN Transactions T ON (E.transaction_id=T.id) 
 where E.account_id = X

The next part is the hard part. I want to find all related transactions, regardless of the account id. First I make a list of all the unique reference numbers I found in the previous result set. Then for each one, I can query all the transactions that have that reference number. Assume that I hold all the rows from the previous query in PreviousResultSet

UniqueReferenceNumbers = GetUniqueReferenceNumbers(PreviousResultSet) // in Java
foreach R in UniqueReferenceNumbers // in Java
     SELECT * 
       FROM Transaction_Entries 
      where transaction_id IN (SELECT * 
                                 FROM Transactions 
                                WHERE reference_number=R

Any suggestions how I can put this into a single efficient query?