Beginning Oracle Database 11g Administration From Novice to Professional

CHAPTER 2 SQL AND PL/SQL 35
The next three solutions, shown in Listing 2-15, use a mechanism called the correlated
subquery to produce the same results as the previous solutions; correlated subqueries
cannot be processed independently of the main query.
Listing 2-15. Status of All Suppliers Who Supply Hammers—Examples of Correlated
Subqueries
Listing 2-16 uses a correlated subquery in conjunction with an aggregate function to
count quote records and determine whether the supplier under consideration supplies
hammers.
Listing 2-16. Status of All Suppliers Who Supply Hammers: An Example of Aggregation