Subquery introduced with an or clause

If a query’s where conditions are connected by or, evaluation stops when any clause evaluates to TRUE, and the row is returned.

This query contains two or clauses in addition to the subquery:

select au_fname, au_lname, title
from titles t, authors a, titleauthor ta
where t.title_id = ta.title_id
and a.au_id = ta.au_id
and (advance > (select avg(advance) 
                    from titles t2
                    where t.type = t2.type)
or title = "Best laid plans"
or price > $100)

Adaptive Server orders the conditions in the query plan to evaluate the subquery last. If a row meets the condition of the or clause, Adaptive Server returns the row without executing the subquery, and proceeds to evaluate the next row.