The SQL Database Essentials 2018

Before you start leaming the technicalities of SQL as a computer language. this chapter wm discuss first what a database is and its fundamental characteristics. You will also be informed why the business world is now driven to gather and manipulate data to bring forth more profitable income.

SQL Database Fundamentals

There are many ways on how to define or describe what a database is. In simple terms, it can be defined as a collection of items that can exist over a long period of time. Think of a calling card holder as a database that contains business cards with different information of people that you know (cg. person’s name. job title, company name. contact number). Another one is a printed telephone directory (more popularly known as the yellow pages) that contains the name. phone number and address of the registered residents living in a particular area.

Some define database more professionally. not just a collection of data. It is described as an organized tool capable of keeping data or information that you can retrieve in an effective and elTicient way when the need arises. It can also be more strictly defined as a self-describing collection of objects that are integrated to one another. When you create representations of these physical or conceptual objects then they will be called records. From the previous example of your calling card holder. if you wish to keep track of your business contacts then you have to assign each business card a specific record. Every record contains multiple information or data, such as individual name. job title, company name and address, phone number and more that you will now call the record’s attributes.

A database does not only contain the data that you need. but also what you call its metadala. This is the information that defines or describes the data‘s structure within the given database (that is why it was defined earlier as a self-describing entity). stored in a region called data dictionary. Thus, data retrieval will be faster if you know how information is arranged and stored. Furthermore. relationships exist among the data items since they are integrated to one another. Check the following figure for a sample illustration of what a database is.
SQL Database essential

Whether a database contains a simple collection of a few records or a massive system composed of millions of records. it can be categorized into three types: personal, workgroup or departmental, and enterprise. Each category is characterized by the database size. the machinery size into which the database runs and how big the organization that manages it.

  1. Personal Database - This is conceptualized and designed by a single person on a standalone computer. Its database structure is rather simple and the size is relatively small. For example, your personal electronic address book. 
  2. Workgroup/Departmental Database- This is designed and created by individuals of a single workgroup or department within a certain organization. The database structure is larger and more complex, as compared to the personal category, which is also accessed by multiple users at the same time.
  3. Enterprise Database- Among the three categories. this type is conceptualized and created to handle the entire flow of infonnation of very large organizations. Thus. the database design i nvolves far more complex structures.   

Relational Database Fundamentals

Taking the discussion further into a more technical aspect. a relational database is an entity consisting of logical units known as tables. This relational database model was first formulated by Dr. E. F. Codd in 1970. How the tables are related to each other defines their relationships. In this scenario. data is simplified into smaller yet more logical and manageable units that optimize the database performance. The following figure shows an illustration on how the various components of a relational database are connected to each other.
sql database server

A table consists of rows and columns that store data. In a relational database. these tables are related to one another improving the data rctrietal process is hen a query is submitted by the user. For you to clearly picture out this idea. convert the information found on the calling card holder into a spreadsheet like a Microsoft Excel tile. Assume that these are your contacts from companies that have ordered products and services front your business.

Database Management Systems

A database management system. or simply DBMS, is an important programming tool that consists of a set of programs that define, manage and process databases and all applications associated to them. Through this, you are able to build a structure and operate on the valuable data that the database holds in a very efficient way. There are two main types of users that work on DBMS the conventional user who retrieves or modifies data and the administrator who is responsible for maintaining the structure of the database.

The following are the key features of a DBMS:
  1. Allows the creation of new databases and their data structures
  2. Allows data query and modification using an appropriate programming language
  3. Allows the storage of vast amounts of data over a long period of time
  4. Enables database recovery in times of failure. error or intentional misuse
  5.  Controls data access from many users at once
It was during the late 1960's when the first commercial DBMS appeared. It evolved from tile systems that basically provided data storage for over a certain period ol'time. Though such systems were capable of storing tremendous amount of data. computer professionals still have to face problems of data loss and an inefficient information retrieval system. There were also issues on control access where errors occur when two users modify the same file at the same time. Some examples of these applications are airline resen ation Systems, banking systems and corporate record keeping systems. among others.

With the advancement of technology in the market today. you can find numerous programs that will be suitable for your DBMS requirements. There are applications that run on a small scale level like your personal computer or tablet. Some are built to run on a large and powerful equipment. like those being used by multinational companies. Nevertheless. the on-going trend is for DBMS to be executed on multiple platforms or machines (whether large or small) that are interconnected to one another. forming an immense scalable network. IT experts have also found ways on how store data using lnternet technology in powerful data centers or more popularly known as clouds. This cloud can be public entity (managed by a large company like Microsolt or Google) or a private one (maintained and stored via the intranet within an organization).

In this chapter you have learnt the essential features of a database and how it transforms to become a relational database. Also, you had an overview of the history and characteristics of database management systems. In the next chapter you will learn the fundamental structure of the SQL language and its components.

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