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Questions tagged [rdbms]

Relational Database Management System, a widely used type of database management system characterised by its extensive use of joining as a core operational principle.

75
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5answers
34k views

Which database could handle storage of billions/trillions of records?

We are looking at developing a tool to capture and analyze netflow data, of which we gather tremendous amounts of. Each day we capture about ~1.4 billion flow records which would look like this in ...
71
votes
6answers
42k views

What are the differences between NoSQL and a traditional RDBMS?

What are the differences between NoSQL and a traditional RDBMS? Over the last few months, NoSQL has been frequently mentioned in the technical news. What are its most significant features relative to ...
33
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6answers
9k views

Why don't databases create their own indexes automatically?

I would have thought that databases would know enough about what they encounter often and be able to respond to the demands they're placed under that they could decide to add indexes to highly ...
30
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5answers
3k views

Is it OK to keep a value which updates in a table?

We are developing a platform for prepaid cards, which basically holds data about cards and their balance, payments, etc. Up until now we had a Card entity which has a collection of Account entity, ...
23
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3answers
21k views

Is it acceptable to have circular foreign key references\How to avoid them?

Is it acceptable to have a circular reference between two tables on the foreign key field? If not, how can these situations be avoided? If so, how can data be inserted? Below is an example of ...
23
votes
1answer
13k views

Using MongoDB and PostgreSQL together

My current project is essentially a run of the mill document management system. That said, there are some wrinkles (surprise, surprise). While some of the wrinkles are fairly specific to the project,...
21
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4answers
5k views

What does “index” mean on RDBMSs? [closed]

I use indexes like most developpers do (mostly on... well ! index), but i'm sure there is a lot of subtle way to optimize a database using index. I'm not sure if it is specific to any implementation ...
19
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5answers
5k views

Is ROLLBACK a fast operation?

Is it true that RDBMS systems are optimized for COMMIT operations? How much slower/faster are ROLLBACK operations and why?
13
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2answers
1k views

NoSQL and RDBMS together?

I was wondering if there are any good solutions for recording data in a NoSQL database and then converting them over to an RDBMS? For example, if you wanted to capture some data quickly, like ...
12
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1answer
4k views

Commit vs Fast Commit vs Commit Cleanout in Oracle Database

I was wondering whether someone could verify my understanding regarding the differences between those 3 terms as pertaining to Oracle Databases. Many sources confuse these terms and do not explain ...
11
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3answers
3k views

Use MySQL to regularly do multi-way joins on 100+ GB tables?

Background: I’ve created a web application that I would like to be able to scale reasonably well. I know I'm not Google or Twitter, but my app uses a fairly large amount of data for each user and thus ...
9
votes
5answers
21k views

Why is optimistic locking faster than pessimistic locking?

Both forms of locking cause a process to wait for a correct copy of the record if its currently in use by another process. With pessimistic locking, the lock mechanism comes from the DB itself (a ...
8
votes
9answers
4k views

Which DBMS are fast enough for an online game (few thousand players)? [closed]

I'm currently making an MMORPG game, which could have a few thousand players online at the same time (probably not; just wishful thinking). First we wanted to use MySQL, but I have heard it isn't fast ...
8
votes
1answer
231 views

Are relations slower than a big, inefficient table?

I've been asked in my job to violate the first normal form (repeating groups across columns, using empty / null values) several times, "for the sake of computer processing power". In a nutshell, a "...
8
votes
2answers
380 views

How to modify an update in Oracle so it performs faster?

I have this query: UPDATE ( SELECT h.valid_through_dt, h.LAST_UPDATE_TMSTMP FROM ETL_FEE_SCH_TMP d, FEE_SCHEDULE_HISTORICAL h WHERE h.FUND_ID = d.FUND_ID AND h....
7
votes
4answers
5k views

Why are so many MPP solutions based on PostgreSQL instead of MySQL?

Astor Data, Greenplum and GridSQL all allow Massive Parallel Processing of SQL queries. They are also all built around PostgreSQL technology. Is this just because of licensing issues or are there ...
7
votes
3answers
27k views

Detecting SQL Server Utilization with a query

My current project will send queries to an sql server constantly and It may use 100% of the memory or CPU. How can I check if the server is nearing full utilization in a stored procedure so that I ...
7
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2answers
2k views

Single Drive vs Multiple Drives

Generally bottleneck of RDBMS (I am a MySQL user) performance is disk access. SSD provides great performance compared with conventional spindle drives. Question : Is it possible to improve ...
7
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1answer
3k views

Full text search through many tables in MySQL

We have high traffic NEWS websites, I want to add a feature that every user can search through over all content of site, such as news, polls, comments, galleries,etc . Each of contents type has its ...
6
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2answers
6k views

A database in MySQL is a schema in Oracle : I do not understand this statement

Please help me understand this statement: A database in MySQL is a schema in Oracle. I have just started to use Oracle and I find it different from other RDBMS softwares I have used like MSSQL, ...
6
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2answers
13k views

Execute system commands in postgresql

My requirement is to execute a system command like (ls) or C program when a trigger executes. Is there any way to create a trigger function to solve this problem.
6
votes
1answer
3k views

Which queries are faster with Postgres than with MySQL InnoDB [closed]

I've read Performance difference between MySQL and PostgreSQL for the same schema/queries. Here is a brief retelling of the article: PostgreSQL tables are heap tables (means no clustered index)... ...
6
votes
2answers
12k views

How to insert values in junction table for many to many relationships?

I have three tables in database: trips(trip_id(pk), trip_name(unique), user_id(fk)) places(place_id(pk), place_name(unique)) trips_places_asc(trip_id(fk), place_id(fk)) Since many trips can ...
6
votes
1answer
592 views

Determining which isolation level is appropriate

This is a homework question. For the following transactions state the isolation level that will maximize throughput without lowering the integrity of the database. Explain the answer. ...
5
votes
2answers
118 views

Does the concept of candidate key exist only in theory?

I know the concept of candidate key in RDBMS theory, but do candidate keys really exist in actual SQL engines? I mean is there any way to designate a particular column or set of columns as a candidate ...
5
votes
1answer
769 views

How to model complex systems like networks in Postgres

I need help with modelling of a network involving switches (24 port, 48 port, POE, and a combination of those) and edge devices (computers, IP cameras, telephones). From an object oriented perspective,...
5
votes
1answer
386 views

Optimised Schema for City-to-City Distance Table

This is my first question, forgive me if this question is simple. I'm stuck here, trying to implement the relationships for the data represented below. I want to scale it vertically (new rows), ...
5
votes
1answer
348 views

CASE, VIEW, CTE or JOIN LATERAL: which is the best approach?

As a follow-up to this question, I have one of my own. The original question concerns the use of a CASE statement with > than 100 options and the statement has to be used in 4 places - so obviously ...
5
votes
3answers
938 views

Which databases support parallel processing across multiple servers? [closed]

I need a database engine that can utilize multiple servers for processing a single SQL query in parallel. So far I know that this is possible with the some engines, though none of them are feasible ...
4
votes
3answers
819 views

How to achieve many to many relationship in this database design?

I am currently working on small travel application in which users can add other users' trips in their wishlist. I am facing difficulty in designing database for wishlist. What I have tried so far is: ...
4
votes
2answers
939 views

SQL Server- Limit to Concurrent table queries?

In SQL Server, or RDBMS systems in general, is there a limit to the number of concurrent queries that can be made against a table? How is it that N number of users can access the same physical data ...
4
votes
3answers
1k views

MySQL very slow query when changing one WHERE field despite no index/key

This is quite a confusing issue for me. I have a database full of baseball statistics. Running this query: SELECT * FROM hits JOIN stadiums ON stadiums.gameName = hits.gameName JOIN players ON (...
4
votes
1answer
563 views

Big Data vs Relational Database on making structure of Data-ware house for telecom data analysis [closed]

I'm currently doing my final year project on telecommunication mining. On starting project I got confuse on choosing database. As data on mobile communication is going on increasing so I think Big ...
4
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1answer
2k views

How mature is the Firebird database when compared with PostgreSQL and MySQL?

I have used PostgreSQL with small projects and MySQL is running in production environment. No issues with them. I have been hearing of Firebird which is again a solid RDBMS in the open-source area. ...
4
votes
1answer
279 views

how much overhead an error in RDBMS has?

I have a class in my project. On the class I need to do two inner select, to know is there any duplication or not, but I think if I get duplication error and then manage that is better than to select. ...
4
votes
1answer
421 views

Postgres heap table performance on SSD

I've read Performance difference between MySQL and PostgreSQL for the same schema/queries.. Is it still relevant with appearance of Solid State Drive? That article said that Postgres is better for ...
4
votes
1answer
2k views

Amazon SimpleDB or Amazon RDS?

I'm at a deciding point in my project of whether to implement the database using SimpleDB or Amazon RDS. The database needs to be accessed through an iPhone app and as well through a website. Here are ...
4
votes
1answer
1k views

Optimizing indexes

I just began optimizing my schemas with indexes (pretty late I guess). I never dealt with huge dataset but I'll be soon coping with about 1 to 5 millions rows. Here is the schema I'm using right now ...
4
votes
3answers
2k views

STARTUP command fails : Why is that?

I just installed Oracle Database Express Edition 11g Release 2.This is the first time I am using Oracle. Earlier I have used MySql and MSSql and I bet this one is a lot different ! These are the ...
4
votes
1answer
1k views

How to Update same table on deletion in MYSQL?

In my Database I have a table: Employee with recursive association, an employee can be boss of other employee. Following is query I used to create table: CREATE TABLE IF NOT EXISTS `Employee` (...
4
votes
1answer
65 views

How much does an ordered query of an attribute costs in terms of operations when the attribute is a key or an attribute?

How much does the following query costs in terms of operations when the attribute is a key or an attribute ? SELECT Attribute FROM R WHERE Attribute = 50 ORDER BY Attribute We assume we ...
3
votes
6answers
1k views

Is normalization process needed?

Well after learning DBMS as a subject i got so many questions in mind. Normalization is one of them. As i learnt it there was a lot more confusion and i found that whatever we do in normalization ...
3
votes
1answer
564 views

Surrogate key / Primary key: Better to use an existing unique data field or create a key field?

I am not sure if this question has been asked or not. At least I couldn't find it. I am curious about a primary key in terms of efficiency with data searching and retrieval. This is a hypothetical ...
3
votes
3answers
3k views

How does an OLAP cube database differ from an RDBMS?

Is a cube database, simply an RDBMS—such as PostgreSQL or MySQL—configured for OLAP via a star or snowflake schema? Or is a cube database different from an RDBMS, and if so how?
3
votes
1answer
5k views

MySQL: What is SQL mode and why we use it

If in an application, if we execute sql_mode=mysql4.0 as a first query in my application but using MySQL 5.1 in my application then what will happen? Will my system use MySQL 4.0 or MySQL 5.1 ...
3
votes
1answer
393 views

Why do we need partitions in PostgresSQL? (or any other RDBMS)

So, I am trying to teach myself partitions in PostgreSQL. I understand that a database can become slow when a table hits millions+ of lines and indexes don't fit into memory anymore. One thing that ...
3
votes
1answer
77 views

Plan for managing financial transactions in an easily and retrievable manner, indefinitely

I've got a large (many columns) MySQL database table (InnoDB) that has a fairly high number of INSERTs (~500/day). Think of the rows as financial transactions. Clients need to be able to view these ...
3
votes
1answer
963 views

Restriction on self referencing on insert in MYSQL?

How to restrict insert on adding self-referencing rows in a recursive relation table (a table contains foreign key points itself)? mysql> SELECT * FROM Employee; +-----+------+-------------+-----...
3
votes
1answer
191 views

Modelling the structure of a database involving products with multiple barcodes

What would be the best way to store barcodes for products? I have a situation where the same product can have many different barcodes, let's say I have 1 product and this product can have 100 ...
3
votes
3answers
3k views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...