Обсуждение: understand basics - multiple cars in a database - selection of one
hello,
I would like to understand the basics of the database architecture:when the application is lunched, I would like to select one car and then every property, option, transaction applicable to this car should be recorded by the application automatically.
basically I'm trying to avoid a menu adding the relevant car every-time a property is changed.
thank you.
On Tue, Feb 4, 2014 at 1:20 PM, avpro avpro <avprowebeden@gmail.com> wrote:
when the application is lunched, I would like to select one car and then every property, option, transaction applicable to this car should be recorded by the application automatically.
basically I'm trying to avoid a menu adding the relevant car every-time a property is changed.
Some clarification: When you select a specific car, what are you expected your application to do? What does, "this car should be recorded by the application automatically" mean?
let me write it differently:
"when the application is lunched, I would like to select one car and then every property, option, transaction (applicable to this car) should be recorded by the application automatically. "
the property, option, transaction should be recorded by the application"when the application is lunched, I would like to select one car and then every property, option, transaction (applicable to this car) should be recorded by the application automatically. "
On 4 February 2014 22:25, Richard Broersma <richard.broersma@gmail.com> wrote:
On Tue, Feb 4, 2014 at 1:20 PM, avpro avpro <avprowebeden@gmail.com> wrote:when the application is lunched, I would like to select one car and then every property, option, transaction applicable to this car should be recorded by the application automatically.
basically I'm trying to avoid a menu adding the relevant car every-time a property is changed.Some clarification: When you select a specific car, what are you expected your application to do? What does, "this car should be recorded by the application automatically" mean?
Start by searching on Amazon for Database design. On 2/4/2014 2:20 PM, avpro avpro wrote: > hello, > > I would like to understand the basics of the database architecture: > I have several cars in a database; > when the application is lunched, I would like to select one car and > then every property, option, transaction applicable to this car should > be recorded by the application automatically. > > basically I'm trying to avoid a menu adding the relevant car > every-time a property is changed. > > how is this happening at database level? > any references available for this example or something similar? > thank you. > John
avpro avpro wrote > let me write it differently: > "when the application is lunched, I would like to select one car and then > every property, option, transaction (applicable to this car) should be > recorded by the application automatically. " > > the property, option, transaction should be recorded by the application > > hope this helps. thanks > > > On 4 February 2014 22:25, Richard Broersma < > richard.broersma@ > >wrote: > >> On Tue, Feb 4, 2014 at 1:20 PM, avpro avpro < > avprowebeden@ > >wrote: >> >> >>> when the application is lunched, I would like to select one car and then >>> every property, option, transaction applicable to this car should be >>> recorded by the application automatically. >>> >>> basically I'm trying to avoid a menu adding the relevant car every-time >>> a >>> property is changed. >>> >> >> Some clarification: When you select a specific car, what are you >> expected >> your application to do? What does, "this car should be recorded by the >> application automatically" mean? >> entity tables: cars; properties; options; transactions relationship tables: cars-properties; cars-options; cars-transactions (this could just be a foreign-key, probably) Application: 1) A Drop-Down populated with data in "Cars" and presented to the user 2) User selects a Car 3) Application uses the CarID associated with the selected car to: 3a) Retrieve all cars-properties records having that CarID 3b) Retrieve all cars-options record having that CarID 3c) Retrieve all cars-transactions (or just transactions) having that CarID Application now has a record of every property/option/transaction associated with the selected car. Retrieve basically means issuing "SELECT * FROM cars-properties|cars-options|cars-transactions WHERE carID = ?" Now, of course you need some way to actually get data onto those tables. Fundamentally that means issuing: "INSERT INTO cars-properties VALUES (carID, propID)" Though you also need to populate both the cars and properties tables first so that the relationship table can be assured of having valid data via foreign key constraints. If you go and add a property to cars-properties that is not already on properties you can either abort and ask the user to add it or automatically add the indicated property first and then add the cars-properties record. Your request supposes knowledge of many different areas of "application development" and "application tiers" (e.g., user-interface[UI], middle-ware, database drivers, PostgreSQL, and database design - to name the most obvious). You should not expect much help from volunteers for such a broad inquiry. Mailing lists like this one best operate on specific usability questions. There are numerous educational materials and institutions available whose purpose is to teach people how to do this kind of thing - though I do not personally have any suitable recommendations and you haven't really described what experience you already possess. David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/understand-basics-multiple-cars-in-a-database-selection-of-one-tp5790571p5790595.html Sent from the PostgreSQL - novice mailing list archive at Nabble.com.
David Johnston wrote > cars-properties Note that typically "properties" of an object/entity are modeled as attributes/columns on the entity table. cars [ carid serial, car_make text, car_model text, car_year text] as opposed to separate tables. That main reason for this is that each property has a specific data type to which correct values must conform. A generic "cars-properties" table would require that all property values be stored as text. Note that it is also valid to define cars like: cars [ carid serial, car_properties hstore|json ] so that the properties are a simple key-value table. A combination of both can work as well. This is where "Database Design" comes into play and as mentioned many excellent books exist on the topic. Once you have a design you then develop whatever UI elements that are needed to properly interact with it. While UI is most important there is ample room for layering and facade-ing that settling for a known sub-optimal database design will likely be painful in the long-run. David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/understand-basics-multiple-cars-in-a-database-selection-of-one-tp5790571p5790597.html Sent from the PostgreSQL - novice mailing list archive at Nabble.com.
This short and quick intro to database design should be helpful in understanding the concepts http://www.datanamic.com/support/lt-dez005-introduction-db-modeling.html
Also, when you say 'recorded' by the app, do you mean displayed by the app on frontend or recorded in the database?
On Tue, Feb 4, 2014 at 4:20 PM, avpro avpro <avprowebeden@gmail.com> wrote:
Johnany references available for this example or something similar?how is this happening at database level?I have several cars in a database;hello,I would like to understand the basics of the database architecture:
when the application is lunched, I would like to select one car and then every property, option, transaction applicable to this car should be recorded by the application automatically.
basically I'm trying to avoid a menu adding the relevant car every-time a property is changed.
thank you.
On Tue, Feb 4, 2014 at 10:34 PM, avpro avpro <avprowebeden@gmail.com> wrote: > let me write it differently: > "when the application is lunched, I would like to select one car and then > every property, option, transaction (applicable to this car) should be > recorded by the application automatically. " > > the property, option, transaction should be recorded by the application > > hope this helps. thanks Oh yes, line feeds definitely made it a lot more understandable! I suppose what you need here is a good mapper for your application (e.g., hibernate, but hey, you did not mention your application language). I suspect you are asking for a lazy master-child table lookup but hey, you did not mention your tables. This could help: http://qt-project.org/doc/qt-4.8/sql-masterdetail.html but I recommend you getting either a better knowledge of your aim or a good SQL/relational theory book. Luca
hi all,
thanks for your feedback. I owe you some answers:
I'm beginner in programming both databases and applications. I'm using PostgreSql and Qt / C++ for my application and I'm trying to learn.thanks for your feedback. I owe you some answers:
On 5 February 2014 10:15, Luca Ferrari <fluca1978@infinito.it> wrote:
On Tue, Feb 4, 2014 at 10:34 PM, avpro avpro <avprowebeden@gmail.com> wrote:Oh yes, line feeds definitely made it a lot more understandable!
> let me write it differently:
> "when the application is lunched, I would like to select one car and then
> every property, option, transaction (applicable to this car) should be
> recorded by the application automatically. "
>
> the property, option, transaction should be recorded by the application
>
> hope this helps. thanks
I suppose what you need here is a good mapper for your application
(e.g., hibernate, but hey, you did not mention your application
language).
I suspect you are asking for a lazy master-child table lookup but hey,
you did not mention your tables.
This could help: http://qt-project.org/doc/qt-4.8/sql-masterdetail.html
but I recommend you getting either a better knowledge of your aim or a
good SQL/relational theory book.
Luca
avpro avpro wrote > hi all, > > thanks for your feedback. I owe you some answers: > I'm beginner in programming both databases and applications. I'm using > PostgreSql and Qt / C++ for my application and I'm trying to learn. > next time I'll come up with a better question. in the end this is a novice > list. or am I on a wrong list? Its as good a list as any though don't set your expectations too high. The majority of volume on these lists are technical questions about how PostgreSQL operates. The ability for any list to answer design philosophy questions is limited (and of diverse opinions) not to mention the fact that there are lots of different programming languages that interface with PostgreSQL and so only a subset of the people monitoring the list are likely to be using your toolkit - even if we all are using PostgreSQL. David J. -- View this message in context: http://postgresql.1045698.n5.nabble.com/understand-basics-multiple-cars-in-a-database-selection-of-one-tp5790571p5790901.html Sent from the PostgreSQL - novice mailing list archive at Nabble.com.