Re: We all are looped on Internet: request + transport = invariant

Good day, Joe.

J> "Fictional" is IMO not a good choice for
J> describing aggregates, because it means "a story that is not true",
J> whereas an SQL aggregate is something that is "true" (in the
J> mathematical sense) but is "derived" from other values.

It means, that TML and DDL aggregates have different sense.

J> (I'm not sure what the special symbols mean -- maybe what you need first
J> is a syntax reference for TML)

http://sql4.by.ru/site/sql40/en/author/tree_eng.htm

J> sum of the employees salaries?

yes.
"amount" is quantity of employees

J> How do I see employees in just one department?

department[id="1"].employee >>;

or

department[name="Technical"].employee >>;

J> How do I see a single employee?

employee[id="31"] >>;

or

employee[name="Tomson"] >>;
-- maybe several employee with surname Tomson

J> How do I see all employees that have a salary greater than 3500

department.employee[salary>3500] >>;

J> ordered by their names?

Now sorting for output is absent.
I'm not sure, that it's necessary,
but i already thought about this and continue to think.

J> How do I actually retrieve SUM(salary)

Declare field "sum" as not fictional.

You can always declare field "sum" as not fictional and
put sign "#" before field to prevent output of field.

J> GROUP BY department?

It is always "group by", because it is field of record "department"

P.S.
If you don't like to put sign "#" before field "sum",
or you don't like absence of sorting NOW
(it's possible, that i add sorting),
then remember, that advantage is absence of gasket
(php, etc) between DBMS and external world.
That is more important for un-experienced users.

Dmitry Turin
http://html6.by.ru
http://sql4.by.ru
http://computer2.by.ru