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.
This article is Part 2 of the Microsoft Access tutorial.
Here’s what’s included in this article:
A primary key is one or more columns that have been configured as the unique identifier field for the table.
Most primary keys are comprised of a single column, but they can also be comprised of multiple columns.
Any value stored in a primary key field is unique to that record. No other record contains that value. The value is a unique identifier.
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.
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:
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.
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 Database, MySQL, FileMaker, PostgreSQL, and more below.
There are 3 types of relationships in relational database design. They are: