Using Derived Relations

¨  More typical is a query against aggregate values

• Example:

“Find the largest total account balance of any branch.”

🞑 Need to compute total account balance for each branch first.

SELECT branch_name, SUM(balance) AS total_bal

FROM account GROUP BY branch_name;

🞑 Then we can easily find the answer:

SELECT MAX(total_bal) AS largest_total

FROM (SELECT branch_name,

SUM(balance) AS total_bal

FROM account GROUP BY branch_name)

AS totals (branch_name, tot_bal);