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Questions tagged [rdbms]

A relational database management system (RDBMS) is a database management system (DBMS) in which data is stored in tables and the relationships among the data are also stored in tables.

A relational database management system (RDBMS) is a database management system () that is based on the relational model as introduced by E. F. Codd, of IBM's San Jose Research Laboratory. Many popular databases that are currently in use are based on the relational database model.

RDBMSs have become a predominant choice for the storage of information in new databases used for financial records, manufacturing and logistical information, personnel data, and much more. Relational databases have often replaced legacy hierarchical databases and network databases because they are easier to understand and use. However, relational databases have been challenged by object databases, which were introduced in an attempt to address the object-relational impedance mismatch in relational database, and XML databases.

History:
The development for the RDBMS model began at in 1974
The first commercially available RDBMS system was in 1979
The first RDBMS system for Mac OS was in 1984

References:

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PostgreSQL IN operator with subquery poor performance

Why is the "IN" operator so slow when used with subquery? select * from view1 where id in (1,2,3,4,5,6,7,8,9,10) order by somedata; executes in 9ms. select * from view1 where id in (select ext_id from aggregate_table …
Snifff
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Should I normalize my DB or not?

When designing a schema for a DB (e.g. MySQL) the question arises whether or not to completely normalize the tables. On one hand joins (and foreign key constraints, etc.) are very slow, and on the other hand you get redundant data and the potential…
Assaf Lavie
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Why don't DBMS's support ASSERTION

So I recently learned about ASSERTION in my databases course, and my prof noted that major databases don't support it, even though it is in the SQL-92 standard. I tried googling to find out why, but there doesn't seem to be any discussion on the…
forivall
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How to solve "Batch update returned unexpected row count from update; actual row count: 0; expected: 1" problem?

Getting this every time I attempt to CREATE a particular entity ... just want to know how I should go about figuring out the cause. I'm using Fluent NHibernate auto-mapping so perhaps I haven't set a convention appropriately and/or need to override…
wgpubs
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Difference between sparse index and dense index

I am very confused to understand the difference between sparse index and dense index. Can you explain the difference between them ?
Sabir Al Fateh
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How do cursors work in Python's DB-API?

I have been using python with RDBMS' (MySQL and PostgreSQL), and I have noticed that I really do not understand how to use a cursor. Usually, one have his script connect to the DB via a client DB-API (like psycopg2 or MySQLdb): connection =…
Nicholas Leonard
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Overnormalization

When would a database design be described as overnormalized? Is this characterization an absolute one? Or is it dependent on the way it is used in the application? Thanks.
emkay
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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?
Bruno Reis
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Can one make a relational database using MongoDB?

I am going to make a student management system using MongoDB. I will have one table for students and another for attendance records. Can I have a key in the attendance table to reach the students table, as pictured below? How?
İlker Dağlı
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How to change a value of a field using MySQL Workbench?

I have installed MySQL Workbench and I have the following problem. I perform this simple select query: SELECT * FROM spring_security.user; that returns a list of rows. So, in the output area, I select a field of a specific row and I try to change…
AndreaNobili
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What's the difference between NoSQL and a Column-Oriented database?

The more I read about NoSQL, the more it begins to sound like a column oriented database to me. What's the difference between NoSQL (e.g. CouchDB, Cassandra, MongoDB) and a column oriented database (e.g. Vertica, MonetDB)?
Tedk
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What is the difference between Primary key and prime attribute?

Is there any difference between primary key (which is a composite key) and a prime attribute?
user3243499
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What are the different types of keys in RDBMS?

What are the different types of keys in RDBMS? Please include examples with your answer.
sikender
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Is this a good way to model address information in a relational database?

I'm wondering if this is a good design. I have a number of tables that require address information (e.g. street, post code/zip, country, fax, email). Sometimes the same address will be repeated multiple times. For example, an address may be…
WW.
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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…
Noah Heldman
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