Relational Database Concepts
An important part of every business is to keep records. We need to keep records of our customers, the employees of our company, the emails etc. To keep all the data indivually is quite difficult and hectic job, because whenever if we need the record of a particular customer or an employee we need to search manually. It takes lot of time and still not reliable. Here comes the concept of databases.
What is database?
A database is an organized collection of information. A simple example of a database are like your telephone directory, recipe book etc.
A Relational model is the basis for any relational database management system (RDBMS). A relational model has mainly three components:
A collection of objects or relations,.
Operators that act on the objects or relations.
Data integrity methods.
To design a database we need three things:
A table is one of the most important ingredient to design the database. It is also known as a relation, is a two dimensional structure used to hold related information. A database consists of one or more tables.
A table contains rows : Rows is a collection of instance of one thing, such as the information of one employee.
A table contains the columns: Columns contains all the information of a single type. Each column in a table is a category of information referred to as a field.
One item of data, such as single phone number of a person is called as a Data Value.
ACID properties are one of the important concept for databases. ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties of a DBMS allow safe sharing of data. Without these properties the inaccuracy in the data will be huge. With the help of the ACID properties the accuracy can be maintained.
Normalization is a design technique which helps the to design the relational databases. Normalization is essentially a two step process that puts data into tabular form by removing redundant data from the relational tables. A basic goal of normalization is to create a set of relational tables that are free of redundant data and the data should be consistent. Normalization has been divided into following forms.
- First Normal Form: A relational table, by definition are in first normal form. All values of the columns are atomic. It means that it contains no repeating values.
- A relationl table is in second normal form if it is in 1NF and every non- key column is fully dependent upon the primary key.
- A relational table is in third normal form (3NF) if it is already in 2NF and every non- key column is non transitively dependent upon its primary key. The advantage of having table in 3NF is that it eliminates redundant data which in turn saves space and reduces manipulation anomalies.