True enough, and if you are only reading, atomicity doesn't matter. But if you want to record answers?
Files are well suited to either read-only uses. But once you start writing, you have the potential for partial updates unless you use a rename or delete to mark the end of the update. Which is done far too seldom. SQL and databases are a skill I recommend for any well-rounded programmer. On Aug 3, 12:18 pm, DanH <danhi...@ieee.org> wrote: > "Further, while with some careful attention to detail, you can get > reliable operation with files, even if the device is turned off at a > bad moment -- too often people don't manage to get it right. (Key idea > - the only atomic filesystem operations are rename and delete). " > > Seems to me that opening a file read-only is fairly atomic. Don't > attempt to modify the questions (or store result data in the same > file) and there's no atomicity problem. > > On Aug 3, 1:48 pm, Bob Kerns <r...@acm.org> wrote: > > > > > I agree. > > > My experience with this sort of thing is that frequently, if you don't > > start out with a SQL database, you ultimately end up having to convert > > it later. So often it's better to start there. > > > Here's why. Using a database scales better. If you end up with a large > > quiz, you'll have to load it all into memory at once -- or split it up > > into lots of files. XML or JSON become the "wasty" approach, as Paul > > put it, beyond a certain point. > > > Further, while with some careful attention to detail, you can get > > reliable operation with files, even if the device is turned off at a > > bad moment -- too often people don't manage to get it right. (Key idea > > - the only atomic filesystem operations are rename and delete). > > > With a database, you still have to think about transactions, but you > > can group any set of operations in a transaction, and there is a > > single, reliable mechanism for reliable transactions. You don't have > > to invent your own. > > > I would definitely use multiple tables. For example > > > Question: > > * id (primary key) > > * answerID (foreign key constraint on answer table, do not chain on > > delete) > > * number (if you want to define a numbering for your questions). > > * text > > > Answer: > > * id (primary key) > > * questionId (foreign key constraint on question table, chain on > > delete -- i.e cause this to be deleted if the question is deleted). > > * number (if you want to control for a consistent order, rather than > > randomize it). > > * text > > > If you're recording the responses: > > > Response: > > * id (primary key) > > * questionID (foreign key constraint on question table, chain on > > delete) > > * answerID (foreign key constraint on answer table, chain on delete). > > > You'll also want to define indexes -- for example, on > > Response.questionID, which should probably also be unique (and > > Answer.questionId, which should not, or Answer.questionId, number, > > which should). > > > Then you can quickly find question #2345098 and its answers, and > > consume no more storage and little more time than if you had just 10. > > > On Aug 3, 6:09 am, "saify.zeenwala" <saifyzeenw...@gmail.com> wrote: > > > > Hi > > > > Better opt for SQL as it would be convenient for you to do further SQL > > > query. > > > where as in property file you have to do manual search and have to do > > > string > > > operation. > > > > create table with 3 columns > > > > question > > > possibleanswer > > > correct answer > > > > Might be this will help you > > > > On Tue, Aug 3, 2010 at 2:19 AM, amos <milan.ku...@gmail.com> wrote: > > > > Hello, > > > > I want to create such application that would show a question to user > > > > and possible 3 (or n) answers and user should pick correct answer > > > > (some kind of learning quiz). I'm not sure about the storage for those > > > > data - questions and possible answers. What would be most natural way > > > > for Android. I know that I can either use property files or tables in > > > > sqlite database. There will be about 500 items (1 question, 3 answers, > > > > 1 correct answer ). > > > > Any ideas? > > > > Thanks > > > > > -- > > > > You received this message because you are subscribed to the Google > > > > Groups "Android Developers" group. > > > > To post to this group, send email to android-developers@googlegroups.com > > > > To unsubscribe from this group, send email to > > > > android-developers+unsubscr...@googlegroups.com<android-developers%2Bunsubs > > > > cr...@googlegroups.com> > > > > For more options, visit this group at > > > >http://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
