Difference Between Inner Join and Outer Join

Edited by Diffzy | Updated on: October 04, 2023

       

Difference Between Inner Join and Outer Join

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Introduction

Both the inner Joins and the Outer joins are two kinds of joins that are significant in SQL. It helps to show data and information about two Common rows or different things based on common things. The difference between the two terms is the inner joins bring back the common rows Between the two tables, but on the other hand the outer joins bring back the works of the inner joins to the things not specified. Inner joins tell about the commonality between the two things and the outer joins tell about the similarities between the two or more things.

There are a total 4 kinds of joins which are as follows -

  • Inner Joins
  •  Outer Joins
  • Right Outer Joins
  • Left Outer Joins

Here we are discussing the two main types of joins: Inner Joins and Outer Joins.

Inner Join

  • It returns and combines the data into one table.
  • It's an intersection operation.
  • Searches‧ data and information for overlapping and Matching Information.
  • It returns or brings back the common things between the two tables.

Outer Joins

  • It combines the data and information from two tables and rows that are not matched and have nil values.
  • It's a Union Operations.
  • It returns the data from the inner joins to the joins which are unmatched.
  • Further, Outer joins are divided into 3 kinds of joins - 
  1. Full Outer
  2. Right Outer
  3. Left Outer

Inner Joins V. Outer Joins

The term Joins is used in SQL. These joins are used to combine information, data, and records and also to manipulate these things from two or more tables to one table. Both the inner and outer ones are different from each other. The difference between the two is how they handle the wrong match conditions. Like the inner join returns the same rows between the two tables, based on a specific Condition. In comparison, the Outer joins returns all the data and information from the database or dataset, even when there is no match.

Difference Between the Inner Joins and Outer Joins in Tabular Form

Basis of DifferenceInner JoinsOuter Joins
DefinitionIt returns the matching row between 2 tables on specific conditions.It returns all the data and records from the database even when there is no match between them.
Types of joins.  Inner joins have only one type.Outer joins have 3 subtypes - Full Outer Joins, Right outer joins, and left outer joins.
Results of the joinsIntersection Between the two tables.It is the union of the two tables.
Matching of tablesIt needs similar data between the two tables.It retrieves the match table from one row and all the rows from another table.
PerformanceIt is slow in comparison to outer joins.It is efficient and fast as compared to inner joins.
The unmatched Row and Usage of the joinsIn this join unmatched rows are omitted.It is used when we want to retrieve what is common between the two tables.Whereas in this type it is filled with null values.It is used when we require all the data and information from both tables.

What is Inner Joins?

SQL or Structured Query Language is a language that is used in programming and it is also used to manage databases and information. The inner joins are types of these SQL. That collects and retrieves data from both tables. A new table is formed by combining these row which has the same values based on commonness.  When an inner circle combines two or more tables it forms new tables that contain the matching rows from the previous two tables. The term Inner join can be used in two forms - Inner joins or joins, both can be used interchangeably.

The inner Join Phrase appears in the table after the from clause in the Structure Query Language or SQL. The Situation to match between the tables A & B is specific and it is after the ON Keyword. This situation is known as the Join Condition, for example - C.n= D.n. The Inner join can attach 3 or more tables if they have a foreign key relationship.

In SQL there are 4 types of joins and inner is one of them. It is used to join 3 or more tables that have something in common. An inner join of C and D will give the result of the intersection between C and D, with the help of a Venn diagram.

Different Types of Inner Joins in SQL

The SQL has different types of joins and inner joins are one of them, here are some of the types of inner joins-

Inner Joins - In SQL, one of the commonly used joins is inner joins. It combines only those tables that have something in common and after that, it makes a new column by combining these common tables

Natural Joins - This is a type of join, where it combines two tables based on common data or information based on similar names or data and information. It also uses an equal sign to join the table, so it is also known as equijoins.

Theta Joins - A join that does not use an equal sign to combine the two tables and instead uses a comparison operator. It uses conditions to join the table, therefore it is also called Conditional Joins

Equijoins - It joins tables based on the equality of two rows and columns. It uses an equal sign to combine the table which is why it is called a Simple join.

The syntax for writing Inner Joins in  Structured Query Language

The syntax is as follows -

SQL

SELECT   column_name (s)

FROM   table 2

INNER JOINS  Table 3

ON  table2. joins columns_names = table3. joins columns_names

In this above SQL, it is shown how inner join is performed by joining tables 2 and 3 which is based on column_name. The select statement is used to choose the column which people want to retrieve from the table. Inner Joins are used to join these two tables and the ON keyword is used to specify the condition.

Meaning of this Syntax

SELECT: It tells us about the column that we want to retrieve which will result from the table.

FROM: shows the first table which we want to combine.

INNER JOINS: It shows the join type which we want to perform.

ON: It shows the condition that we want to use to join the tables.

table 2: It shows the first table that is to be joined.

table 3: It shows the second table that is to be joined.

column_name: It shows the column that we want to use to join the tables.

Here are some examples of inner joins:

Example:  There are  two tables, Customers and Orders, with the following information:-

Customers table:

Customer_idFirst_nameLast_name
3RahulSeth
4RajSharma
5PranavVerma

Orders table:

Order_idCustomer_iditem
13Washing Machine
24AC
35Speaker

Now, to join the Customers Id and Orders tables with their matching fields customer_id, we use the following SQL   Query:-

SQL

SELECT  Customers.customer_id, Order. it

FROM     Customers

INNER JOINS  Orders

ON  Customers.customer_id=  Orders.customer_id

What are Outer Joins?

In SQL, there is a type of joins that joins data and records from the two tables and that also includes rows that do not match with each other from the tables. It reclaims all the rows from one table and similar rows from the other table. If the table consists of no matching rows then all the tables that are not matched still be included with null values.

Types of Outer Joins

There are 3 kinds of Outer joins, these are the following -

  • Full Outer Joins
  • Right Outer Joins
  • Left Outer Joins

Fuller Outer Join - It recovers all the rows from both tables. It also includes the rows which do not match either of the tables. If a table does not contain any row which is matched, the result will include all the rows from the table given with null values.

Right Outer Join - It recovers all the rows from the right table, and from the left table it includes the matching rows. When there are no matching rows on the left side table, then it also includes rows from the right table, and with null values from the left table.

Left Outer Join - It brings back all the rows from the left table and matches one from the right table. If no row matches in the right table, the result will still include all the rows from the left table with null values from the right table.

Difference Between the Inner Joins and Outer Joins in Points

Here are a few differences between inner joins and outer joins -

  • Inner joins are joins that return only the rows that have matching values in both tables or more than two tables. Whereas, Outer joins are the joins that return all the rows from one table and the other tables the matching ones.
  • The inner join returns a set of results that only contain matching rows, whereas the outer joins return all the rows from one of the tables and the matching rows from the other tables.
  •  The inner joins have one type only, but on the other hand, the outer joins have 3 types of joins these are - Full Outer joins, Right Outer Joins, and Left Outer Joins.
  • While using the syntax the inner joins use the keyword - INNER JOIN. While the outer joins use the Keywords such as - FULL OUTER JOIN, RIGHT OUTER JOINS, LEFT OUTER JOINS.
  •  The matching rows, where the inner joins need must be matching rows in both tables. On the other hand, outer joins do not need any matching rows in both tables.
  •  Inner joins do not hand back the NULL values. On the other hand, the outer joins return the values NULL for not matching rows.
  •  Inner joins are more efficient than Outer Joins. On the other hand, Outer Joins may include data that is mismatched or irrelevant.
  • Inner Joins improve the accuracy of the data by removing the irrelevant or data that is not mismatched. Whereas the Outer Joins might include the mismatch data and also irrelevant data.
  •  Inner Joins are used when the rows are to be retrieved only for the matching rows from the tables. On the other hand, the outer join is used when someone wants to retrieve all the rows from one table and matching rows from the other tables

Conclusion

Both the terms Inner joins and Outer joins are two important types of joins used in Structured Query Language or SQL. It helps us to combine data and information from two or more tables. Inner joins retrieve only the rows that are matching from both tables, while on the other hand, the outer joins return all the rows from one table and matching rows from the other one. Outer joins include the values NULL for the rows that are not matching, and they can be less structured than the inner joins. The Inner joins help to improve data accuracy by removing irrelevant data that is mismatched, while on the other hand the Outer joins may include mismatched data and data that is not accurate. The Inner joins are used when someone wants to return or retrieve the matching row only from two tables, while Outer joins are used when we want to return each of the rows from one table and rows matching other tables. The difference between the two joins can be found in differences like their Meanings, Definition, Matching, Set, Results, Rows, NULL values, Data Accuracy, Data, etc., which has been explained above.

References

  • https://www.Scaler.Com/topics/internal-be part of-vs-outer-be a part of/
  • https://www.Geeksforgeeks.Org/internal-join-vs-outer-be a part of/
  • https://www.Freecodecamp.Org/information/square-be part of-kinds-inner-join-vs-outer-be a part of-instance/


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"Difference Between Inner Join and Outer Join." Diffzy.com, 2024. Fri. 19 Jul. 2024. <https://www.diffzy.com/article/difference-between-inner-join-and-outer-join>.



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