The reason i need to join these two kinds is because i need to know the department name that the employee works at as you can see the query "List all employees's Id (EmployeeId), name (Name), salary (Salary) and their department name (DepartmentName) for the ones earns more than 8000 US dollar".
In SQL, i could do the query like this: select e.EmployeeId, e.Name, e.Salary, d.DepartmentName from Employee e, Department d where e.Salary > 8000 That is why i need to join these two kinds. Bruce On Jun 16, 1:26 pm, "Ikai Lan (Google)" <[email protected]> wrote: > It's not clear to me why you need a join here. If you're just doing it by > Department type, why not make the "Department" field a String? > > Ikai Lan > Developer Programs Engineer, Google App Engine > Blog:http://googleappengine.blogspot.com > Twitter:http://twitter.com/app_engine > Reddit:http://www.reddit.com/r/appengine > > > > On Thu, Jun 16, 2011 at 3:30 PM, Bruce Aloe <[email protected]> wrote: > > Hello, > > > In a simple case, suppose i have two kinds (tables) stored in GAE > > datastore: > > > Employee (EmployeeId, Name, Salary, StartDate, DepartmentId) > > Department(DepartmentId, DepartmentName) > > > For Employee kind, EmployeeId is the unique key and DepartmentId is > > the join attribute for Employee to make join with Department kind. For > > Department kind, DepartmentId is the unique key. Both Employee and > > Department kinds have quite a lot of tuples, let us say, more than 3 > > million tuples. > > > There is a need to make join query over both Employee and Department > > kinds in order to answer the query concerns the data from both kinds. > > For example a query could be "List all employees's Id, name, salary > > and their department name for the ones earns more than 8000 US > > dollar". > > > How can i make join query among different kinds to answer the query > > concerns different kinds? > > > Of course, there could be more than just two kinds stored in GAE > > datastore. If one wants to make join query among more than two kinds, > > how to handle that? > > > Thank you for your help! > > > Bruce > > > -- > > You received this message because you are subscribed to the Google Groups > > "Google App Engine" group. > > To post to this group, send email to [email protected]. > > To unsubscribe from this group, send email to > > [email protected]. > > For more options, visit this group at > >http://groups.google.com/group/google-appengine?hl=en.- Hide quoted text - > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
