Gain insights into fundamental database concepts, relational databases, and entity-relationship diagrams. Learn about normalization techniques and basics of SQL to enhance database efficiency.

Databases are universal - they underlie the technology you use every day. They're a crucial component of everything from telecommunications systems, banking systems, and video games to just about any other software system that maintains some amount of persistent data.

In this course, you'll learn about the fundamental concepts of databases, why and when they're used, what relational databases are, and entity-relationship diagrams. You will also be exposed to techniques like normalization that help to increase the efficiency of databases. You'll wrap up with a look at the basics of Structured Query Language (SQL). 

After completing this course, you will be able to move onto more advanced courses involving database systems and SQL.

Database Design Fundamentals for Software Engineers

# SQL data types

A SQL data type is an attribute that specifies the type of data of any object. You can specify the data type of each column in the table based on your requirements.

Some of them are listed below:

## Exact Numeric Data Types

| Data Type    | Ranges From   |  To   |
| --- | --- | --- |
|  int   |  -2,147,483,648	   |  2,147,483,647  |
|  bigint   |  -9,223,372,036,854,775,808   | 9,223,372,036,854,775,807     |
|  smallint   |  -32,768   |  32,767   |
|  tinyint   | 0    |  255   |
|  bit   |   0  |  1   |
|  decimal   |  -10^38 +1	   |  10^38 -1 |
|  numeric   |  -10^38 +1	   |  10^38 -1 |

## Approximate Numeric Data Types

| Data Type    | Ranges From   |  To   |
| --- | --- | --- |
|  float   |  -1.79E + 30   | 1.79E + 308  |
|  real   |  -3.40E + 38 | 3.40E + 38|

## Date and Time Data Types

| Data Type    | Ranges From   |  To   |
| --- | --- | --- |
| datetime   |  Jan 1, 1753	   | Dec 31, 9999|
| smalldatetime	 |  Jan 1, 1900 |  Jun 6, 2079 |
|  date   |  Stores a date like June 30, 1991 | - |
|  time   | Stores a time like 12:30 P.M.
 | - |

## Character Strings Data Types

|  DATA TYPE  |  Description    |
| --- | --- |
|  char  | Maximum length of 8,000 characters.( Fixed length non-Unicode characters)    |
| varchar | Maximum of 8,000 characters. (Variable-length non-Unicode data).    |
| varchar(max)  | Maximum length of 2E + 31 characters, Variable-length non-Unicode data.   |
|  text  | Variable-length non-Unicode data with a maximum length of 2,147,483,647 characters.   |

# What is an operator in SQL?

An operator is a reserved word or character used primarily in a SQL statement's [WHERE](https://www.educative.io/courses/database-design-fundamentals/the-where-clause) clause to perform operation(s), such as comparisons and arithmetic operations. These operators are used to specify conditions in a SQL statement and to serve as conjunctions for multiple conditions in a statement.

## SQL arithmetic operators

Assume variable 'a' holds 10 and variable 'b' holds 20.

|  Operator   |  Description |  Example |
| --- | --- | --- |
|  + (Addition)	   |  Adds values on either side of the operator   | a + b will give 30 |
|  - (Subtraction)	   |  Subtracts right-hand operand from left-hand operand   | a - b will give -10 |
|  * (Multiplication)	   | Multiplies values on either side of the operator    |  a * b will give 200 |
|  / (Division)	   |  Divides left-hand operand by right-hand operand   |  b / a will give 2 |
|  % (Modulus)	   |  Divides left-hand operand by right-hand operand and returns remainder   | b % a will give 0 |

## SQL comparison operators

Assume 'variable a' holds 10 and 'variable b' holds 20.

|  Operator   |  Description   | Example    |
| --- | --- | --- |
|  =   |  Checks if the values of two operands are equal or not, if yes then condition becomes true |  (a = b) is not true  |
|  != | Checks if the values of two operands are equal or not, if values are not equal then condition becomes true  | (a != b) is true |
|  <> | Checks if the values of two operands are equal or not, if values are not equal then condition becomes true | (a <> b) is true |
|  >  | Checks if the value of the left operand is greater than the value of right operand, if yes then condition becomes true | (a > b) is not true |
| <   | Checks if the value of the left operand is less than the value of right operand, if yes then condition becomes true |(a < b) is true |
| >=  | Checks if the value of the left operand is greater than or equal to the value of right operand, if yes then condition becomes true | (a >= b) is not true |
|  <= | Checks if the value of the left operand is less than or equal to the value of right operand, if yes then condition becomes true | (a <= b) is true  |


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You don't have to worry about these terms too much as we will be using them in the lessons to come, which will help you to understand how they are used. In the next lesson, we will discuss SQL constraints. 




In this lesson, we will learn about the different data types supported by SQL.

Introduction

Fundamental Concepts

Data Modeling

Entity-Relationship Data Model

The Relational Data Model

Functional Dependencies

Normalization

Structured Query Language

Conclusion

SQL Data Types and Operators

SQL data types