Все вопросы: [rdbms]

147 вопросов

похожие теги: rdbms-agnostic
1
голосов
9ответов
3850 просмотров

Database "pointers" to rows?

Is there a way to have "pointers to rows" in a database? for example I have X product rows, all these rows represent distinct products but many have the same field values except their "id" and "color_id" are different. I thought of just duplicating the rows but this could be error prone, plus m...

1
голосов
3ответов
5806 просмотров

Can Excel use itself as a Database?

I found an interesting article at MSDN, which says: ADO makes it possible to treat an Excel workbook as if it were a database. So is it possible for an Excel workbook to connect to itself, and treat one of its worksheets as a database table and execute queries on it? -- and is this possibl...

-1
голосов
3ответов
226 просмотров

Good Java application to learn OOD

I'm looking for an open source java application (C# application is also ok), to learn & understand good Object Oriented design. Specifically, I'm looking for interactions with relational database, so that I can understand the finer details between converting an OO design to non-OO structure....

17
голосов
7ответов
14526 просмотров

How universal is the LIMIT statement in SQL?

I'm in the process of generalizing a Django DB replication app and it uses the statement: SELECT %s FROM %s LIMIT 1 to fetch 1 row and use the Python DBAPI to describe the fields, it works fine with ORACLE and MySQL but, how cross platform is the LIMIT statement?

1
голосов
1ответов
1150 просмотров

Spring RDBMS vs JDBCTemplate

How much of a performance difference is there between these two models? What kind of reasons are there for using one over the other? In my application I am using a lot of the same statements over and returning both Objects and primitives. There are a few oracle stored procedure calls and perfo...

5
голосов
6ответов
1423 просмотров

Choosing between a directory server (a.k.a LDAP database) and an RDBMS

In my project, where I'm the lead developer, we earlier had a network configuration that was stored a single XML file. The configuration contains info about a network layout - its constituent hosts, various details about each host like OS, platform, users configured in each them, several attribut...

1
голосов
1ответов
1941 просмотров

Microsoft SQL Server to Oracle Data Migration (Conversion) (Other RDBMS ok, too)

Can you please give some tips or guidelines, best practices for MicroSoft SQL server to Oracle Data Migration? IMHO, it is something that comes best with experience. So I would like to benefit from your experience. Please share any insights that you have into design, modeling, testing or tuning f...

23
голосов
8ответов
18523 просмотров

How to store data with dynamic number of attributes in a database

I have a number of different objects with a varying number of attributes. Until now I have saved the data in XML files which easily allow for an ever changing number of attributes. But I am trying to move it to a database. What would be your preferred way to store this data? A few strategies I ...

0
голосов
1ответов
148 просмотров

simplest fail over support for standard rdbms?

Currently I am working on failover support of an existing application. The application uses postgres to store data but does not use any special feature (view/trigger etc). The database is more of a configuration storage rather than real data storage. When the application starts, it loads the da...

0
голосов
2ответов
232 просмотров

How to represent a self to self relationship in rdbms?

Hopefully this is a silly question but my brain is fried and I can't think of how to do it right now. I'm messing around trying to make a social networking thingy and will need to keep track of a person's "followers". I have a user table made already, but how do I represent the idea of users bei...

22
голосов
10ответов
7958 просмотров

Is there an official name for the many-to-many relationship table in a database schema?

Most of the projects I've worked on have required many-to-many relationships in the database schema. For example, you might have the concept of Users and Groups, and the database might contain a table User, a table Group, and a table UserGroup to relate the two. I'm interested in the conceptual...

10
голосов
7ответов
11135 просмотров

Why is Select 1 faster than Select count(*)?

In Oracle, when querying for row existence, why is Select 1 fast than Select count(*)?

5
голосов
2ответов
4739 просмотров

What does Codd's 'non-subversion rule' mean?

Recently I was reading about Codd's 12 Rules, and I understood all except number 12, the 'non-subversion' rule. If anyone can explain me the rule (using an example, preferably), that would be very helpful. Thanks.

33
голосов
8ответов
13717 просмотров

Why aren't OODBMS as widespread as RDBMS?

Why are relation databases more common than object-oriented databases? If the Object Oriented Programming paradigm is so widespread, shouldn't we see lots of OODBMS? Wouldn't they perform better than the RDBMS+OR/M?

7
голосов
11ответов
841 просмотров

Help me to connect inheritance and relational concepts

I was talking with a programmer pal of mine about inheritance and its use in designing models. He's a big proponent and I'm a little more tepid. Mostly because I tend to design systems from the bottom up: Database -> Application -> Presentation (honestly, I'm not much of a front-end guy, so...

3
голосов
1ответов
126 просмотров

RDBMS data-relation burden

Our in-house system is built on SQL Server 2008 with a 40-table 6NF schema. Most of the tables FK to 3 others, a key few as many as 7. The system will ultimately support 100s of employees working with 10s of 1000s of customers and store 100s of 1000s of transactional records -- prime-time acces...

5
голосов
3ответов
11627 просмотров

The difference between a 'view' and 'base' relation

What is the difference between a 'view' and 'base' relation in database systems?

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1ответов
306 просмотров

About RDBMS Concept

Can any give me overview of Entity,attribute,Tuples and Domain set. and E-R Model Diagram and 1st,2nd and 3rd Normalforms.

65
голосов
7ответов
36298 просмотров

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 a...

1
голосов
3ответов
1276 просмотров

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 = ? A...

0
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2ответов
1106 просмотров

What algorithms do RDBMS use?

What are the main algorithms used in RDMBS ?

2
голосов
2ответов
175 просмотров

Switch values between rows in unique column

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 the row with id=2 to foo, and the row with id=1 to bar? I know you could probably just assign temporary names to both then stick in the desire...

4
голосов
2ответов
106 просмотров

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?

15
голосов
1ответов
3548 просмотров

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 da...

2
голосов
2ответов
1883 просмотров

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 store...

1
голосов
2ответов
440 просмотров

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 ...

1
голосов
5ответов
259 просмотров

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 t...

10
голосов
3ответов
3143 просмотров

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 -- j...

25
голосов
10ответов
10546 просмотров

Как думать на SQL?

Как мне перестать думать о каждом запросе в терминах курсоров, процедур и функций и начать использовать SQL так, как он должен быть? Делаем ли мы переход к мышлению на SQL только на практике или есть какое-то волшебство в изучении языка запросов на основе наборов? Что вы сделали для перехода?

12
голосов
5ответов
8809 просмотров

Помогите мне включить терминологию Oracle в терминологию SQL Server

Моя компания теперь впервые поддерживает Oracle, и большинство моих коллег - разработчики SQL Server, которые на самом деле не работали с Oracle. Я немного знаком с Oracle, но далеко не гений в этом вопросе. К сожалению, этого достаточно, чтобы означать, что я знаю об Oracle больше, чем большинс...