What does the rollback statement do exactly?
Rollback is used to reach the previous commit, but what will it do exactly? ...
rdbms
Table-agnostic Foreign Keys?
So, a simple question. First, I did read this StackOverflow question, so no need to point me towards it. I'm working on a similar problem right now. Specifically, I have a database with an Auditing table that is used to store auditing info about other tables within the db. The basic form of this table is: ID, EntityID, EntityTypeID, Ac...
What RDBMS command is used to tell what user has what permissions on a particular object?
What RDBMS command is used to tell what user has what permissions on a particular object? ...
Caching moderate amounts of data in a web app - DB or flat files?
A web app I'm working on requires frequent parsing of diverse web resources (HTML, XML, RSS, etc). Once downloaded, I need to cache these resources to minimize network load. The app requires a very straightforward cache policy: only re-download a cached resource when more than X minutes have passed since the access time. Should I: S...
Schema considerations when moving from an RDBMS (MySQL) to Solr
Whilst testing a Solr install for a future MySQL -> Solr migration, it's immediately apparent that the "rules" for what constitutes a good data stucture, and by extension an efficient search, are very different in Solr when compared to an RDBMS like MySQL. The most obvious thing being that data isn't (or doesn't seem to be) normalised to...
Help me put Oracle terminology into SQL Server terminology
My company is now supporting Oracle for the first time, and most of my colleagues are SQL Server developers who haven't really worked with Oracle. I'm a little bit familiar with Oracle, but far from a genius on the subject. Unfortunately, that is enough to mean that I know more about Oracle than most of my co-workers, so I find myself ...
OVER clause in Oracle
What is the meaning of the OVER clause in Oracle? ...
Can Keys and Keyrefs be spread across multiple XSD files?
I'm trying to mimic a relational database structure using XML. (Just in case anyone is wondering why, my reasons for using XML are: (1) The total amount of data is expected to be small, (2) I need non-programmers to be able to edit some of the input tables, and (3) I want the installation process to be as simple as possible (i.e., no da...
How to think in SQL?
How do I stop thinking every query in terms of cursors, procedures and functions and start using SQL as it should be? Do we make the transition to thinking in SQL just by practise or is there any magic to learning the set based query language? What did you do to make the transition? ...
Concurrent DB connection pool in Haskell
I am a Java programmer who learns Haskell. I work on a small web-app that uses Happstack and talks to a database via HDBC. I've written select and exec functions and I use them like this: module Main where import Control.Exception (throw) import Database.HDBC import Database.HDBC.Sqlite3 -- just for this example, I use MySQL in produ...
Was anyone thinking of 'CLR Server' instead 'SQL Server'?
I was thinking many times, now days that we have Linq and other CLR language-specific built-in search, sort and other capabilities over tables, collections and object, why not have the 'SQL Server' or rather call it 'CLR Server' (not only OOP Server but CLR 3.5) which will be a CLR (or COM) DLL that exposes the data allowing users linqin...
How to load text file (txt/csv) into a database table (Windows) - looking for an RDBMS independent solution
Hi all, I am looking for a generic way to load flat/text files (txt/csv) into a database table in a .Net application. So far I know that... 1) I could MSSQL BCP - but that's MS SQL Server only 2) Use the JET engine to access flat files (pain with schema.ini file etc. as file names frequently vary) 3) Load txt/csv file into a .Net array...
Implementing a virtual list in Java
I need to fetch many records from an RDBMS in Java (10-20k) my target system expects them to be available as Java List. So I want to implement my code as "Virtual list" where I actually only fetch the records I actually need. I expect SQL like SELECT * FROM CUSTOMER WHERE COUNTRY="Moldovia" as parameter and just return what is requeste...
How to persist a complicated, nested object with JPA
I'm working on a project which parses information with a NLP library from classified ads on internet forums. After the processing I have ForSaleItem instances and all sorts of details like condition, price etc. When I call the toString() method on these objects, it does not return a string stored in the object itself but rather looks up...
When should you use JCR and when should you use JPA/RDBMS?
The Java JCR API defines a persistence mechanism which can be used to replace many of the traditional roles of a RDBMS. For example, JackRabbit - the JCR reference implementation - supports transactions, SQL queries, object-content mapping, etc. You could pick one or the other, storing binary data in BLOBs/file system pointers in a RDBM...
Does aliasing tables names in large queries have noticeable impact on performance?
Does aliasing tables names in large queries have noticeable impact on performance? Aliasing: ... ... FROM table_1 T1 ... ... ... Is it significantly different for the various DB systems out there? ...
If you have a db table with a unique column (like "name"), how would you go about switching the names of two rows? (Using Hibernate, but it sounds like a problem across the board)
Let's say you had a table like this /------------ | id | name | |------------| | 1 | foo | | 2 | bar | ----------- There is a uniqueness constraint on the 'name' column. How would you set #2's name to foo, and #1's name to bar? I know you could probably just assign temporary names to both then stick in the desired names,...
What algorithms do RDBMS use?
What are the main algorithms used in RDMBS ? ...
In SQLite3, will this select statement benefit from two indexes?
I am using a DBD::SQLite in memory database. I have defined the following indexes for a table: CREATE INDEX x ON ss (a, b); CREATE INDEX y ON ss (c, d, e, o); Will the following select statement use these two indexes? SELECT f, g FROM ss WHERE a = ? AND b = ? AND c = ? AND d = ? AND e = ? And, I should only make indexes on those co...
When to use CouchDB vs RDBMS
I am looking at CouchDB, which has a number of appealing features over relational databases including: intuitive REST/HTTP interface easy replication data stored as documents, rather than normalised tables I appreciate that this is not a mature product so should be adopted with caution, but am wondering whether it is actually a viabl...