Relations in Queries

In the travel expense accounting example there is a 1:n relationship between the Employee and the Travel classes.


class Employee



    IList travels;



Now Suppose you want to find all employees who traveled with the purpose "TechEd 2006". The NDOql query for this is

travels.Purpose LIKE 'TechEd 2006'

which is converted to the following SQL query

SELECT Employee.* FROM Employee, Travels

WHERE Travels.Purpose LIKE 'TechEd 2006'

AND Employee.IDemployee = Employee.ID

As you can see you don’t have to bother with Join-queries in NDOql.

The keyword OID allows to specify Id-columns as names in query expressions:

ObjectId oid = SomeObject.NDOObjectId;


Query q = pm.NewQuery(typeof (Employee), "OID = {0}");