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Difference between inner and outer join. i am using two table and want to fetch data from both table so which type join we should use owning of that we can solve our problem

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Let’s understand what exactly is “INNER JOIN” and “OUTER JOIN”, then we’ll gradually understand the differences between them:

INNER JOIN

Definition:  Inner Join is also known as Natural Join. The result-set of an Inner Join is the commonality between the two or more tables. So, Inner Join always compares two or more tables and combines the matching rows or tuples in the combined tables. It’s also referred to as the default type of join because we write join clause without using any inner keyword and it performs Natural Join. So, if you write Join clause without mentioning Outer Keyword then also it’ll perform the inner join.

Have a look at this video to understand the INNER JOIN in detail.

Example:

There are two tables Table A: Employee Table and Table B: Department Table. Now let’s understand what is the result after performing Inner Join on these Table.

Employee_ID

Name

Department_ID

Salary

5110

Joseph

HR

30,000

5111

Harry

MN

45,000

5112

Scarlet

OP

27,000

5113

Peter

CC

30,000

5114

Haely

TC

35,000

5115

James

HR

33,000

5116

Roobina

MN

47,000

5117

Lily

OP

29,000

Table A: Employee

Department_ID

Department_name

HR

Human Resource

MN

Management

OP

Operation

TC

Technical

SC

Sales

 Table B: Department

Query:

SELECT Name, Salary, Department_name

FROM Employee INNER JOIN Department ON Employee.Department_ID= Department.ID.

Name

Salary

Department_name

Joseph

30,000

Human Resource

Harry

45,000

Management

Scarlet

25,000

Operation

James

33,000

Human Resource

Haley

35,000

Technical

Roobina

47,000

Management

Lily

29,000

Operation

 Result of Inner Join.

Outer Join

Definition: In Outer Join, only those rows are given as output that has the same attribute values in both the tables which are getting compared. The result of Outer Join is all the tuples of both the table.

Outer Join is of three following types:

1.      Left Outer Join

2.      Right Outer Join

3.      Full Outer Join.

 Let us understand the types of Outer Join one by one.

1.      Left Outer Join: This keyword returns all the records from the left table (table1) and the matched records from the right table (table2). If there is no match, then the result is NULL from the right side in the resultant table.

Head over to this video to understand LEFT OUTER JOIN in detail.

 Let’s consider the above Employees and Department Table for example to understand the resultset of the LEFT OUTER JOIN:

Query:

Select Name, Department_name From Employee Left Outer Join Department ON Employee.Department_ID=Depoartment.ID.

Left Outer Join’s Result: All the tuples from Employee Table are displayed in the result.

Name

Department_name

Joseph

Human Resource

Harry

Management

Scarlet

Operation

Peter

Null

Haely

Technical

James

Human Resource

Roobina

Management

Lily

Operation

2.   Right Outer Join: This keyword returns all records from the right table (table2), and the matched records from the left table (table1). If there is no match, the result is NULL from the left side.

For more information you can refer to this video:

Let’s consider the above Employees and Department Table for example to understand the resultset of RIGHT OUTER JOIN:

      Query:

Select Name, Department_name From Department Right Outer Join Student ON Employee.Department_ID=Depoartment.ID.

Right Outer Join’s Result: All the rows from the Department table are displayed.

Name

Department_name

Joseph

Human Resource

Harry

Management

Scarlet

Operation

Haely

Technical

James

Human Resource

Roobina

Management

Lily

Operation

Null

Sales

3.  Full Outer Join: This keyword returns all the records when there is a match in either left (table1) or right (table2) table rows (records).

You can also refer to this video for detailed information about Full Outer Join:

Let’s consider the above Employees and Department Table for example to understand the resultset of the FULL OUTER JOIN:

Query: 

Select Name, Department_name From Employee Full Outer Join Department ON Employee.Department_ID=Depoartment.ID.

Full Outer Join’s Result: All the tuples from both the tables are included in the result.

Name

Department_name

Joseph

Human Resource

Harry

Management

Scarlet

Operation

Peter

Null

Haely

Technical

James

Human Resource

Roobina

Management

Lily

Operation

Null

Sales

Now, let’s compare the Inner Join and Outer Join Based on some parameters:

Comparison

Inner Join

Outer Join

DB(Database)

The size of the database returned by Inner Join is smaller than the Outer Join

This returns a comparatively larger database.

Types

No Type

Left Outer Join, Right Outer Join and Full Outer Join

Fundamental

Inner Join returns only the matching rows from both the table.

This returns all the rows from both the tables.

 

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