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Questions tagged [relational-database]

A relational database is a database consisting of relation variables (which are also called *relvars*, *R-tables* or just *tables*). The definition, manipulation and integrity rules of relational databases are based on relational operations equivalent to or similar to the Relational Algebra and Calculus. Relational database principles are the basis of a substantial part of data management theory and practice.

A relational database is a database consisting of relation variables (which are also called relvars, R-tables or just tables). The definition, manipulation and integrity rules of relational databases are based on relational operations equivalent to or similar to the Relational Algebra and Calculus. Relational database principles are the basis of a substantial part of data management theory and practice.

Targeted Questions

This tag is appropriate for questions concerning the relational model, relational and relational database implementation.

The SQL language is commonly used to specify relational database-designs and to define and solve relational database problems. However, DBMSs based on SQL are by definition not s and therefore not all SQL questions are relevant to the relational database tag. Questions specific to or its implementations should be tagged accordingly.

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A Simple One-To-Many Relationship in JPA on Google App Engine

Even after reading the documentation, I seem to have a fundamental misunderstanding about Google App Engine's entity groups. My goal is a trivial example of ORM: I've got some Employees assigned to Departments. An employee can only be assigned to…
Erik R.
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SQL - Delete and subquery

The following is a sql query which I wrote to delete all records in the placement table where the placement.op_number = a list of returned records. The subquery works fine alone and returns only the OP_NUMBER column (with two rows). The error I get…
Markus
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MDR clarification

Setup: I have a MDR relationship as shown below: Event --< Attendee >-- Contact There is a trigger on EVENT that fires before insert and before update that calculaes the number of attendees (by searching for the number of occurances of the…
PartOfTheOhana
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Composite primary key or guid for merging databases

I have scenario like this: I have many machines and there is database on each. There is also one client machine that can pull data from all machines and add to his local database (it could have data from previous download). So tables on `many'…
userbb
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What makes access to OLAP Cubes / Datamarts and similar datastructures, faster than to relational databases?

What makes access to OLAP Cubes/Datamarts and similar datastructures, faster than to relational databases? EDIT A bounty of 200 will be provided asap.
Skippy Fastol
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EntityFramework and aspnetdb

I'm trying to use entity framework together with the default membership "aspnetdb" database. I'm having trouble with membership and user tables, since I'd like to have a navigational property from membership to user. I feel like I've tried every…
Dynde
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Database Design: How to allow for peer orders aka Model a baseball trading card trade

I am stumbling when it comes to how to deal with a database design. I have looked around and found examples like http://www.tomjewett.com/dbdesign/dbdesign.php?page=manymany.php which would work quite well for a shop selling items but I want to…
Mark
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Batch processing fails in Oracle. Find out which statement in the batch is causing it

I am extracting data from excel sheet and inserting them into my oracle table. The database is setup in a way that when executing a batch statement, if any insert statement in the batch fails, all the other statements in the batch are not executed.…
Susie
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SQL Datetime Not Equal To Is Not Working

I have a database consisting of a Customer, Product, and Transaction table. I'm trying to write an SQL statement to list all customers' names and SSN's for those customers who have made no transaction in the year 2000. The TransactionDate column in…
user994585
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How to approach deletion anomalies?

"There are circumstances in which the deletion of data representing certain facts necessitates the deletion of data representing completely different facts. The "Faculty and Their Courses" table described in the previous example suffers from this…
Travis J
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Understanding a one-to-many relationship with MySQL

I have a table users with primary index userId. Currently, each user has a field arrayOfRelatedUserIds, so that any one user can have a relationship with several other users. (It's an array in JSON format). This I know to be not the best solution,…
Snowman
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Back end for iOS app with relational databases

I am currently trying to build an ios application that will need to be able to retrieve and store data in a remote relational database. I have investigated using RestKit for the front end, which seems adequate. I have experience developing with both…
Jay Hack
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Mysql Join inner join left join Multiple Tables null on right table

how to display multiple tables in mysql, i want to display some data such as: table1.autono, table1.name, table1.date. table1 on right table i dont see data thank you for your help SELECT table1.autono, table2.number_reg, table3.no_auto,…
Anshell
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is this relation in third normal form?

I was wondering, is the following relation in 3rd normal form ? USER (username:String PrimaryKey, userType:String, fname:String, lname:String, dateOfBirth:TimeStamp) and userType can be one of the following…
Ali Salehi
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Database Design: One to many of different types

The work flow for something is as follows 1) Create a "Message of the Day" for a particular group of users (which must be approved before active) 2) Assign who can approve this by selecting single users, and/or users who are admins of the group…
user1215399
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