I would recommend also looking at some data warehousing articles as versioning is related to that. Though I do not have any concrete to recommend :-(. Peter
2009/7/9, Alessandro Bottoni <alexbott...@yahoo.it>: > Donald McLean ha scritto: >> Actually, this is a question that I have previously considered for a >> project that I am starting. >> >> My thought was to have an identity column (value assigned by the DBMS) >> and a separate ID column. From here, you can do several different >> things: >> >> 1. Have a "version" column. Use the max function to find the current >> version, or make the current version -1 or something else easy to >> find. >> 2. Use the max function on the identity column to find the latest version. > > I thought about this mechanism but I'm not completely convinced it would > be the right one. I mean, there are two different "user views" to take > into account: > > 1) The user view onto the whole database while browsing/searching for a > specific record. > 2) The single-record view used to examine/edit a specific record. > > While it is easy to use a SELECT with MAX to get the latest version of a > specific record, it is not clear how I could get only the most recent > version of every single record to build up the "browse" view. It looks > like I should use a nested SELECT: first, select all matching records > and, second, select the latest version of each of them. A little bit > messy... > >> 3. Have "previous" and "next" columns with the identity values of the >> appropriate objects in the chain. The current version would have a >> null "next". > > Nice approach! Actually, I did not think about this possibility. Many > thanks for this suggestion. > > This would simplify a lot the SELECT operation used to generate the > "browse" view (just select all of the records that have a NULL > "next-version" field) while maintaining the possibility to go back and > forth between versions (and build up a list of them, if needed). > > I think I will experiment with this one. > >> There are probably other approaches that I haven't thought of. > > I thought about triggers/procedures, as well, but I had the feeling they > would have the same problem as the SELECT + MAX approach. > >> I have used and recommend Hibernate. It simplifies things immensely >> IMO, though it does have its quirks (some of which are not properly >> explained by the documentation). It also works well with a number of >> other DBMS (if changing is something that might happen later). > > Thanks. I'm new to Hibernate, as well, so I'm going to ask you (all) > which book is best for learning Hibernate. I browsed a little bit on > Amazon's but I did not find anything to be enthusiastic about. What > would you suggest me as a good starting point/introductory book? > > Any good web article/tutorial to signal, as well? > > Thanks again. > -- > > Alessandro Bottoni > Website: http://www.alessandrobottoni.it/ > > "In mathematics you don't understand things. You just get used to them." > -- John von Neumann >
