Slide 16.17: Navigating with path expressions (cont.)

Navigating with Path Expressions (Cont.)

Determine the names of the presidents of manufacturers producing blue vehicles.

SELECT v.manufacturer.president.name
  FROM v IN vehicle WHERE v.color = 'blue';

The variable can be omitted if only one class is contained in the from-clause and appears only once.

SELECT manufacturer.president.name
  FROM vehicle WHERE color = 'blue';

Search for the names of presidents of companies with head offices in Detroit.

SELECT president.name FROM company
  WHERE headoffice.location = 'Detroit';

Search for vehicles whose manufacturer’s name is the same as the name of the company's president.

SELECT * FROM vehicle
  WHERE manufacturer.name = manufacturer.president.name;

Know whether an employee named Brown is employed in the Detroit subsidiary of the Ford company.

SELECT emplno FROM company, subsidiary, subsempl, employee
  WHERE company.name = 'Ford'
    AND company.companyID = subsidiary.companyID
    AND subsidiary.location = 'Detroit'
    AND subsidiary.companyID = subsempl.companyID
    AND subsidiary.namesubs = subsempl.namesubs
    AND subsempl.empl = employee.emplno
    AND employee.name = 'Brown';

⇓ from relational SQL to object-oriented SQL

SELECT e FROM e IN employee, c IN company, s IN subsidiary
  WHERE c.name = 'Ford'
    AND s IN c.subsidiary
    AND s.office.location = 'Detroit'
    AND e IN s.employee
    AND e.name = 'Brown';