How to build query to give daily balance across bank accounts? (to then plot in a graph)

Question

How would one build a query to give daily balance across bank accounts? (to then plot in a graph)
Assumptions:
* There is a table TRANSACTIONS which includes columns TRANS_DATE, AMOUNT and BANK_ID. It does NOT include a column for balance. So current balance for a bank account is the sum of the AMOUNTs for that BANK_ID for example. Balance on date XX will be the sum
of all AMOUNTS for that BANK_ID for all TRANS_DATE's prior and including the date XX.
* There is not necessarily transactions on every day for each bank
* Table BANKS which has BANK_ID and TITLE
Would like a query that gives: Supply StartDate and EndDate for the query:
Date Bank1Balance Bank2Balance Bank3Balance TotalBalance
1/1/15 $100 $200 $100 $400
1/2/15 $200 $200 $100 $500
etc

Answer 1

You'll find examples of queries for computing balances in various contexts in Balances.zip in my public databases folder at:
https://onedrive.live.com/?cid=44CC60D7FEA42912&id=44CC60D7FEA42912!169
If you have difficulty opening the link copy its text (NB, not the link location) and paste it into your browser's address bar.
The queries in this little demo file return balances per transaction, however, whereas you appear to wish to return balances at close of business per day.  This can easily be done by means of a subquery which sums all transactions to date.  To return
balances for all dates regardless of whether or not any transactions have been undertaken on the day, an auxiliary calendar table can be introduced into the database to plug the gaps,  The Calendar.zip file in my same OneDrive folder has means of generating
such a table.
With the introduction of an auxiliary calendar table into the database a query can then be written to return the balance per customer at close of business per day over the period 2009 - 2012 covered by the data in the Transactions table:
SELECT CustomerID, Firstname, LastName, calDate,
   (SELECT SUM(TransactionAmount)
     FROM Transactions
     WHERE Transactions.CustomerID = Customers.CustomerID
     AND Transactions.TransactionDate <= Calendar.calDate) AS Balance
FROM Calendar,Customers
WHERE calDate BETWEEN #2009-01-01# AND #2012-12-31#
ORDER BY CustomerID, CalDate;
Rows for each customer/date are returned by means of the Cartesian product of the Calendar and Customers tables (the latter analogous to your Banks table), and the subquery returns the balance at close of each day by correlating the Transactions table with
the Customers and Calendar tables, returning the sum of all transactions per customer up to and including the date in question.  In this example credit and debit transactions are expressed as positive and negative values in a single column of course,
but where separate credit and debit columns are used its merely a case of summing (Credit-Debit), as done in some of the examples in my demo.
To return the data in a horizontal format per date I'd suggest the use of a report which returns one row per date, and within it a multi-column subreport in across-then down column layout, linking the subreport to the parent report on the date columns.
Ken Sheridan, Stafford, England