BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Primay Key Allocation in remote client Master/Slave relation          BorlandTalk.com Forum Index -> Delphi Databases (Multi-Tier) View previous topic :: View next topic   Author Message Geoff Marshall Guest Posted: Tue Jan 17, 2006 6:38 pm    Post subject: Primay Key Allocation in remote client Master/Slave relation What is the vogue method of allocating a primary key to a new slave entry of a master slave relation (or even a new master primary key) in a remote client that is working off line? Geoff Marshall Back to top Geoff Marshall Guest Posted: Tue Jan 17, 2006 11:03 pm    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Loe, Thanks for your comments but I'm not convinced, or I don't understand. Assigning negative values on the client is straight forward, but the article is confusing in its use of the Delta table. If this is a true table (as inferred) then two users could easily be adding values to it at the same time so the lookup would fail. i.e. user A has child -1 which equates to proper key 123456 user B has child -1 which equates to proper key 123457 user A has child -2 which equates to proper key 123458 user B has child -2 which equates to proper key 123459 etc. User A now updates the master which contains foreign key -1. An interesting situation? The article offers an alternative which is to obtain proper keys at update time on the client. I was concerned with this only because it means scanning the master to insert the proper key once for each child record that is assigned a proper key. In my case the amount of data on the client is likely to be small so I may be able to manage this. Are there any more eloquent solutions? Geoff Marshall Back to top Leif Eirik Olsen Guest Posted: Wed Jan 18, 2006 12:58 pm    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela "Geoff Marshall" <ng (AT) nospam (DOT) co.uk> skrev i melding news:43ce1a64$1 (AT) newsgroups (DOT) borland.com... Quote: What is the vogue method of allocating a primary key to a new slave entry of a master slave relation (or even a new master primary key) in a remote client that is working off line? In a master-detail relation (on the client) I assign negative integers to the primary key, and to the foreign key in the detail data on the client. When applied to the server I search/replace negative integer with the desired values. http://bdn.borland.com/article/0,1410,20847,00.html The article shows how to deal with autoinc fields using Midas, but I think it also answares your question. hth. regards, Leo Back to top Bill Todd Guest Posted: Wed Jan 18, 2006 2:31 pm    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Delta and Data are properties of the ClientDataSet. They exist only in local memory and each ClientDataSet has its own private Delta and Data that is not shared with anyone or anything. -- Bill Todd (TeamB) Back to top Kostas Terzides Guest Posted: Wed Jan 18, 2006 6:02 pm    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Geoff Marshall wrote: Quote: Are there any more eloquent solutions? Geoff Marshall Just make sure that master and detail are in a nested dataset structure (server side linkning). This way the delta is common (it is actually a deltatree) for both the master and the detail dataset and the updating is wrapped (automatically) in a transaction. If this is not the case (or if you have to define multiple dataset relations in client side and deal with primary and foreign key values), then you might take a look at 2 components I made that simplify the updating procedure: http://cc.borland.com/Item.aspx?id=23068 Kostas. Back to top Bill Todd Guest Posted: Wed Jan 18, 2006 7:07 pm    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela This is very confusing because you have the terminology backwards in some cases. In a one-to-many relationship the table on the "one" side is commonly called the parent or master and the table on the "many" side is commonly called the child or detail table. Therefore, the table that contains the foreign key is the child or detail table. In your description the lookup table is the master and the data table is the detail table. You need to apply the master (lookup) table changes first so you can get the foreign key value for the detail (data) table records before you apply them. It would help to know what database you are using. -- Bill Todd (TeamB) Back to top Geoff Marshall Guest Posted: Thu Jan 19, 2006 2:58 am    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela I'm beginning to think I don't understand this solution because it is a solution to a different though similar problem. And some of the problem may be the nomenclature. I have a Master table which contains four Foreign Keys pointing to four Lookup tables. Consider just one of these lookup tables. If for example I add five new records to the Master and in doing so I add three new records to the lookup table (i.e. several master records point to the same lookup table). I then want to save these to the server. I apply updates for the lookup table and the records are assigned "proper" key values by the server. I am assuming that I set poPropogateChanges true and the Delta part (the visible part) of the Client Data Set is updated. (I believe this destroys the relation between the Master Table and the Lookup Tables). How do I now apply updates to the Master table? Geoff Marshall Back to top Bill Todd Guest Posted: Thu Jan 19, 2006 3:04 am    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Geoff Marshall wrote: Quote: The database is Interbase. One solution with InterBase is to call SELECT GEN_ID(SOME_GENERATOR, 1) FROM RDB$DATABASE to get the new key and assign it to the records before you call ApplyUpdates. -- Bill Todd (TeamB) Back to top Geoff Marshall Guest Posted: Thu Jan 19, 2006 3:06 am    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Kostas, From the description it looks as if your components are better suited to what I need. I'll have a look a them tomorrow. Thanks Geoff Back to top Geoff Marshall Guest Posted: Thu Jan 19, 2006 5:35 am    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Bill, I'm happy with that definition. So then I have four master tables sharing one detail table. In this design of course the user selects which master the detail is going to belong to by selection from the master data set. If their desired master record does not exist then a new master will be introduces and the detail attached to it. The database is Interbase. Geoff Back to top Geoff Marshall Guest Posted: Thu Jan 19, 2006 1:47 pm    Post subject: Re: Primay Key Allocation in remote client Master/Slave rela Bill, Thanks, that is the solution I was going to try later today. I really only wanted to know if there was a better approach. 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