[jBoss-User] Find optime Database for my Job

[Marco]

I'm involved in a project using Windows 2K, JBoss and a Database. I'm in trouble because few stuffs don't work like I want. I need a free Database that offers concurrent access and nested queries. I built my multi-tier application using InstantDb since my need of a concurrent access was born later. But InstantDb was too slow and I wanted to change. I used Hypersonic SQL and mySql but both of them don't allow nested queries. This is a trouble for me 'cause in JBoss I can't use COUNT, MAX, MIN seen that I can write only where clause and order by section in queries. In order to fix this trouble I changed my queries using structures like the following: instead of -- SELECT MAX(fieldname) FROM tablename -- that can not be set in finder methods, I used -- SELECT fieldname FROM tablename WHERE fieldname = (SELECT MAX(fieldname) FROM tablename) -- that can be! But when I changed database, using Hypersonic and mySql, I discovered I can use that kind of queries with new databases. So I have two different solution: 1) Ask you to extend tags in finder methods in jaws files in order to support use of MAX, MIN, COUNT, DISTINCT, etc. In this way JBoss shoul offer a way to build the first section of sql statements too! I think it should not be an impossible stuff! In this way I could came back to use first statement I wrote with every database I want! Let me know if you agree with me when I say it should be a good improvement. Lat me also know if you need an hand in doing this! 2) Change Database I tried to do this but I had this troubles with: JDataStore: there's no mapping in defaultjaws.xml; Oracle: it's free for developer but hard to install and configure! And I don't have all of this time! DB2: I think its too hudge!! PostgreSQL: Does a version for Windows exist? And I don't know anything about their performances. Of course I want to improve my application performances!!! What do you reccommend to me? What database do you think I should use? What about other databases you offer type-mapping for in defaultjaws?   Let me know if you have any idea that could be interesting for me. Thank a lot,   Eng. Marco Pappalardo Ergotech System Inc.