Slide 16.11: Access to sets of objects

Desired Properties (Cont.)

Access to Sets of Objects (Cont.)

It is possible to name sets of objects.

myfamily := SELECT p FROM p IN person
  WHERE name = myname;
SELECT name FROM myfamily WHERE age > 50;

It should be possible to use in the from-clause any kind of collection that can be derived from the database. Searches for the names of manufacturers of blue vehicles.
SELECT name FROM ( SELECT manufacturer FROM vehicle WHERE color = 'blue' );

The use of collections in queries can be extended to where-clause. Determines the number of companies whose presidents‘. annual salary exceeds 200,000 dollars.
SELECT count(f) FROM f IN company WHERE president IN ( SELECT a FROM a IN employee WHERE salary > 200000 );