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Learn/SQL/SQL Tutorial

SQL•SQL Tutorial

SQL Self Join

Concept visual

SQL Self Join

Pointer walk

two pointers

left=0

right=6

1

3

Start at both ends

Overview

A self join is a regular join, but the table is joined with itself.

Self Join Syntax

Select

column_name(s)

From

table1 T1, table1 T2 WHERE condition

T1 and

T2 are different table aliases for the same table.

Demo Database

Below is a selection from the "Customers" table:

CustomerID

CustomerName

ContactName

Address

City

PostalCode

Country

Alfreds Futterkiste

Maria Anders

Obere Str. 57

Berlin

12209

Germany

Ana Trujillo Emparedados y helados

Ana Trujillo

Avda. de la ConstituciÃ³n 2222 MÃ©xico D.F. 05021

Mexico

Antonio Moreno TaquerÃa

Antonio Moreno

Mataderos 2312

MÃ©xico D.F. 05023

Mexico

SQL Self Join Example

The following SQL statement matches customers that are from the same city:

Loading lesson path

Learn/SQL/SQL Tutorial

SQL•SQL Tutorial

SQL Self Join

Concept visual

SQL Self Join

Pointer walk

two pointers

left=0

right=6

1

3

Start at both ends

Overview

A self join is a regular join, but the table is joined with itself.

Self Join Syntax

Select

column_name(s)

From

table1 T1, table1 T2 WHERE condition

T1 and

T2 are different table aliases for the same table.

Demo Database

Below is a selection from the "Customers" table:

CustomerID

CustomerName

ContactName

Address

City

PostalCode

Country

Alfreds Futterkiste

Maria Anders

Obere Str. 57

Berlin

12209

Germany

Ana Trujillo Emparedados y helados

Ana Trujillo

Mexico

Antonio Moreno TaquerÃa

Antonio Moreno

Mataderos 2312

Mexico

SQL Self Join Example

The following SQL statement matches customers that are from the same city: