SQL: Derived Relations

SQL-92 allows a subquery expression to be used in the from clause.

If such an expression is used, the result relation must be given a name, and the attributes can be renamed.

Find the average account balance of those branches where the average account balance is greater than $1,000.

 select bname, avg-balance


             from (select bname, avg(balance)


                                           from account


                                           group by bname)


                                           as result(bname, avg-balance)


where avg-balance > 1000

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