Introduction

Briefly, a database is the collection, organization, and presentation of information.

It makes it manageable to evaluate an organization’s goal. It allows research into the outcome.

Record keeping is not a recently invented methodology. It comes with human evaluation. Historically, our ancestors collected and organized data to maintain their ideas.

Today, we prefer to collect, record, and organize data to input, process, and output it, so various methods exist for collecting and organizing information.

Table: 1.1 Example of Database Table

SN	Name	City	Country
1	Tom	Toronto	Canada
2	Jack	Parth	Australia
3	Thompson	New York	Thompson
4	Samita	Kolkata	India
5	Chayo	Bejing	China

A brief introduction to SQL terminology


Database: A logical container for data. Entity: An object, such as a person, a car, a song, or a video Attributes: A characteristic of an entity; an example is a model of a car The term datatype refers to the type of data or attribute. For example, varchar, date, and integer. Column: The column contains values. It belongs to a specific field or entity. Row: It is complete information about a specific entity. Record: All information about the entity is a record.

Data Type

The data type in a database specifies the type of data that can be stored and manipulated within the databaseIt defines the values that a variable or attributes allow and the process that can be performed on those values. Data types help ensure data integrity and optimize data storage and processing.

Expression:

An expression is a kind of variable, constant, operator, and function that evaluates to a single value. Expression is executed by performing calculations, making decisions, and manipulating data.

String

String data types are used to store a set of characters such as letters, numbers, words, sentences, symbols, and even paragraphs. In order to handle text information such as name, address, phone no, and other text information, string data types are essential.

Table 1.2: String Data Types

Data Type

Description

Contain type (bytes)

Length Size (bytes)

Storage (bytes)

Example

Character (Char)

Fixed string length size

letters, numbers, and special characters

0–255

1-8000

CHAR(5)

Variable Character (Varchar)

Variable string length size

letters, numbers, and special characters

0–65,535

1-8000

Varchar(10)

Variable Character (Varchar (Max)

Variable string length size

letters, numbers, and special characters

0–2,147,483,647

1-8000

Varchar(MAX)

Data Type	Description	Contain type (bytes)	Length Size (bytes)	Storage (bytes)	Example
Character (Char)	Fixed string length size	letters, numbers, and special characters	0–255	1-8000	CHAR(5)
Variable Character (Varchar)	Variable string length size	letters, numbers, and special characters	0–65,535	1-8000	Varchar(10)
Variable Character (Varchar (Max)	Variable string length size	letters, numbers, and special characters	0–2,147,483,647	1-8000	Varchar(MAX)

Numeric

In SQL, numerical data types are used to store numbers that can be manipulated mathematically. Various arithmetic operations can be carried out on these data types, including addition, subtraction, multiplication, and division. The following categories can be applied to numerical data types:

Table 1.3: Numeric Data Type

Data Type	Descreption	Contain type	Length Size	Storage	Example
Integer	Allow to storing whole numbers without decimal points	Whole number	-2,147,483,648 to 2,147,483,647	4 bytes	Example_Age int
DECIMAL	Allow to storing fixed number of digits after the decimal point	Real number	p=65 and d=30 defult p=10 and s=0	1-9=510-19=9 20-28=13 29-38=17	Example_Price DECIMAL(5, 2) DECIMAL[(P[,S])] * P = PRECISION *S=SCALE

Date and Time

Date and time data types store information related to dates, times, and timestamps. They allow for various operations and analyses on date and time values.

Table 1.4: Data and Time Data Types

Data type	Description	Format	Range	Example
DATE	Allow to store year, month and day	YYYY-MM-DD	'1000-01-01' to '9999-12-31'	2020-12-26
TIME	Allow to store time	HH:MM:SS	-838:59:59' to '838:59:59	12:12:12
DATETIME	Date and time information allow to store	YYYY-MM-DD hh:mm:ss.	'1000-01-01 00:00:00' to '9999-12-31 23:59:59'	2020-12-26 12:12:12
TIMESTAMP	Store date, time and zone information	YYYY-MM-DD hh:mm:ss. UTC	'1000-01-01 00:00:00' UTC to '9999-12-31 23:59:59' UTC	2020-12-26 12:12:12, LA

There are sample questions about the database. It could be true-false or multiple-choice. It helps to know about databases before diving into the course.

It might also be beneficial to you as a learner.