Tag: relationships

What’s the Difference between a Graph Database and a Relational Database?

Graph databases have been gaining popularity over recent years as a viable alternative to the relational model. Graph databases are particularly well suited to storing connected data – data with lots of interconnected relationships, especially those that run many levels deep.

This article looks at the main differences between graph databases and relational databases.

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Database Tutorial (Part 2) – Relationships, Adding Data, Querying Databases

This article is part 2 of the database tutorial.

Here, we cover:

  • Relationships
  • The different ways of adding data to a database
  • Querying a database

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Database Tutorial

This database tutorial is for beginners. It explains basic concepts and assumes no prior knowledge of databases.

You don’t need to follow along – there aren’t any exercises. But there are plenty of screenshots and a few diagrams. The purpose of the tutorial is to introduce you to the basic concepts of databases.

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Microsoft Access Tutorial (Part 2): Design View, Field Properties, & Relationships

This article is Part 2 of the Microsoft Access tutorial.

Here’s what’s included in this article:

  • Design View.
  • Add field properties to a field.
  • Add two more tables (for the relationship)
  • Set up a relationship between three tables.

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What is a Primary Key?

A primary key is a column that has been configured as the unique identifier field for the table.

Any value stored in a primary key field is unique to that record. No other record in that column contains that value. The value is a unique identifier.

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What is a Foreign Key?

A foreign key is a field that is linked to another table‘s primary key field in a relationship between two tables.

In relational database management systems, a relationship defines a relationship between two or more tables. That is, the data in one table is related to the data in the other. One table contains the primary key and the other table contains the foreign key.

When we establish a relationship between the tables, we link the foreign key with the primary key. From that point on, any value in the foreign key field should match a value from the primary key field in the other table.

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What is a Relationship?

In relational database design, a relationship is where two or more tables are linked together because they contain related data. This enables users to run queries for related data across multiple tables.

Relationships are a key element in relational database design.

Here’s an example:

Diagram of one-to-many relationship

Example of one-to-many relationship.

In the above example, the City table has a relationship with the Customer table. Each customer is assigned a city. This is done by using a CityId field in the Customer table that matches a CityId in the City table.

While it’s certainly possible to store the full city name in the Customer table, it’s better to have a separate table that stores the city details. You can easily use a query to look up the CityName by using the CityId that’s stored for that customer.

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What is an RDBMS?

RDBMS stands for Relational Database Management System.

An RDBMS is a particular type of DBMS that uses a relational model for its databases. An RDBMS therefore enables you to create relational databases.

Relational database management systems have become the most popular type of database system. Most major database management systems are relational. Popular examples include Microsoft Access, SQL Server, Oracle DatabaseMySQL, FileMaker, PostgreSQL, and more below.

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The 3 Types of Relationships in Database Design

There are 3 types of relationships in relational database design. They are:

  • One-to-One
  • One-to-Many (or Many-to-One)
  • Many-to-Many

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