You mean rename a department? Yes you will have to loop though all employees in the department and change the records.
But I imagine its a pretty rare event, how often does a department change? So performance isnt a issue. Just run a batch job. Maybe a task, using a cursor to fire a continuion task if still more. On Fri, Jun 17, 2011 at 9:18 PM, Renan Mobile <[email protected]> wrote: > Hi Barry Hunter! > If the user wants to change the Department? How should it be? Change the > name from all Employee? > > Thanks very much for this discussion! > Em 17/06/2011 16:46, "Barry Hunter" <[email protected]> escreveu: > >> >> I think Ikai means, that you dont really need a 'Department' table. >> >> Just store "DepartmentName" directly as a string on your Employee model. >> >> >> In a RDBS you traditionally 'normalize' - mainly to reduce database size. >> >> >> In appengine and the datastore, you denormalize. Disk-space is 'cheap' >> so duplicating the string in every record is not really an issue. >> >> http://en.wikipedia.org/wiki/Denormalization >> >> >> Appengine is based on the premise of write once, read many, to making >> your queries 'lightweight' is important too. Completely eliminating a >> join makes the query much quicker to run. >> >> >> >> (unless you need to query on DepartmentName then you should make it as >> not-indexed, otherwise it will eat up space in the indexes) >> >> >> >> On Fri, Jun 17, 2011 at 4:21 PM, Bruce Aloe <[email protected]> wrote: >> > 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. >> > >> > >> >> -- >> 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. >> > > -- > 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. > -- 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.
