rdbms

What does the term "Tuple" Mean in Relational Databases?

Please explain what is meant by tuples in sql?Thanks.. ...

Object Oriented Database Vs object Relational Database

Hi, I wonder how Object Oriented data modeling is different from Object Relational data modeling? Is it something like the pluses of both object oriented and relational data modeling were clubbed to achieve object relational data modeling? cheers ...

Hidden Features of PostgreSQL

I'm surprised this hasn't been posted yet. Any interesting tricks that you know about in Postgres? Obscure config options and scaling/perf tricks are particularly welcome. I'm sure we can beat the 9 comments on the corresponding MySQL thread :) ...

What is a cluster in RDBMS?

What is a cluster in RDBMS?Thanks. ...

good books / sites on set theory

I'm trying to understand E.F.Codd's "A Relational Model of Data for Large Shared Data Banks" paper. I would like some suggestions on books / sites on set theory. ...

What the best way to handle categories, sub-categories - hierachical data?

Duplicate: SQL - how to store and navigate hierarchies If I have a database where the client requires categories, sub-categories, sub-sub-categories and so on, what's the best way to do that? If they only needed three, and always knew they'd need three I could just create three tables cat, subcat, subsubcat, or the like. But wh...

Circular database relationships. Good, Bad, Exceptions?

I have been putting off developing this part of my app for sometime purely because I want to do this in a circular way but get the feeling its a bad idea from what I remember my lecturers telling me back in school. I have a design for an order system, ignoring the everything that doesn't pertain to this example I'm left with: CreditCa...

Looking for data integration tool

Hi, I was wondering what ETL tool you would recommend as middleware, ETL, to create data transformation between multiple relational databases, flat and other type of files. Ideally, we are looking for windows based software which is flexible enough to work with different databases and platforms should we switch to a different rdbms. I h...

Using Lucene like a relational database

I am just wondering if we could achieve some RDBMS capabilities in lucene. Example: 1) I have 10,000 project documents (pdf files) which have to be indexed with their content to make them available for search. 2) Every document is related to a SINGLE PROJECT. The project can contain details like project name, number, start date, end dat...

How do you resolve a many-to-many collection entity in a RDBMS?

I'm trying to model artists and songs and I have a problem where I have a Song_Performance can be performed by many artists (say a duet) so I have an Artist_Group to represent who the songs is performed by. Well, I now have a many-to-many relationship between Artist and Artist_Group, where an Artist_Group is uniquely identified by the...

Testing across multiple DBMS vendors

Take this query: SELECT * FROM MyTable WHERE MyColumn = 'SomeValue' ORDER BY SomeFakeQualifier.MyColumn DESC It seems that SqlServer just ignores the qualifier in this case. Should you add a JOIN, then it will consider it. This really isn't an issue, until you want to make your queries viable across DBMS vendors. Oracle, f...

Is it possible to create a deadlock with read-only access?

I have a VB6 application accessing a single table on a MSSQL2000 server via ADO. I'm using read-only access (adOpenStatic, adLockReadOnly) There are other applications in the network which do make changes to the table. For some reason I'm getting errors about my application being chosen as a deadlock victim. I'm really confused: Why c...

Freeform Reporting tool

I am looking for free form reporting tool. Free/open source is preferred. It should work without a data source and one should be able to print at any place on a page. I need this because I am using an age old but very fast semi RDBMS which does not support concept of Data Set, Data Source, etc. that as required by all reporting engin...

Data corruption in PostgreSQL timestamp field

I have a PostgreSQL table with the following schema - CREATE TABLE test ( id serial NOT NULL PRIMARY KEY, username varchar(100) NOT NULL, -- The user name dob timestamp with time zone NOT NULL -- The date of birth ); I then inserted some data into the table with data like this - INSERT INTO "test" ("username", "dob") VALUES (E'...

Constituents of a good relational database design

What are the constituents of a good relational database design? I'd want to ask this question in a bit unusual way, lets see if anyone likes the idea. Also read on to see how it's not a duplicate of the question about DB design best practices (or any other question for that matter). The idea is that as a result of voting we will have co...

RDBS when to use complex indexes for queries and when use simple?

Suppose I have table in my DB schema called TEST with fields (id, name, address, phone, comments). Now, I know that I'm going to perform a large set of different queries for that table, therefore my question is next, when and why I shall create indexes like ID_NAME_INDX (index for id and name) and when it's more efficient to create separ...

Main Memory DB vs Object DB

I'm currently trying to pick a database vendor. I'm just seeking some personal opinions from fellow database developers out there. My question is especially targeted towards people who: 1) have used Main Memory DB (MMDB) that supports replicating to disk (hybrid) before (i.e. ExtremeDB) or 2) have used Versant Object Database and/...

Relational & Object-Oriented Database which one is better, will be suppressed?

I wonder if RDBMS or OODBMS will be suppressed in near future? Today I read quite a few articles about differences in both of them and most of the articles seem to favor OODBMS. Does that mean that RDBMS will be suppressed by, not yet well developed, OODBMS? If not, what makes you think so? ...

How to transform SQL table of data into table of pointers ?

Let's say I have an SQL table of tuples (id, lastname, firstname, occupation) where all values are strings (ok, obviously id is a key). I want to transform it to a table with tuples (id, lastid, firstid, occupid), where I only keep pointers to other tables that contain the actual values. I apologize if the example domain of names and oc...

SQL update statement construction - effects on efficiency

If you submit an update statement to a RDBMS in which the order of the column_name = value mappings don't match the physical layout of the file, does it affect (theoretically) the efficiency of the update operation? I ask mainly out of curiosity, knowing full well that there's probably little effect. ...