SQL - INNER JOIN

The SQL INNER JOIN keyword is used to combine column values of two tables and returns all rows from both of the tables when there is a match between the columns.

Syntax

The syntax for using INNER JOIN keyword is given below:

SELECT table1.column1, table1.column2, table2.column1, table2.column2, ...
FROM table1
INNER JOIN table2
ON table1.matching_column = table2.matching_column;

Example:

Consider database tables called Employee and Contact_Info with the following records:

Table 1: Employee table

Table 2: Contact_Info table

• To inner join Employee and Contact_Info tables based on matching column EmpID, the SQL code is given below. This will fetch Name and Age columns from Employee table and Address column from Contact_Info table.

  SELECT Employee.Name, Employee.Age, Contact_Info.Address 
  FROM Employee
  INNER JOIN Contact_Info
  ON Employee.EmpID = Contact_Info.EmpID;
  

  
  

  This will produce the result as shown below:

  Name	Age	Address
  Marry	24	XXX, Brooklyn, New York, USA
  Jo	27	XXX, Grenelle, Paris, France
  Kim	30	XXX, Geuzenveld, Amsterdam, Netherlands
  Huang	28	XXX, Yizhuangzhen, Beijing, China

• To fetch all fields of a table, table.* keyword is used, for example - to fetch all fields of the Employee table, Employee.* is used in the below SQL code:

  SELECT Employee.*, Contact_Info.Address 
  FROM Employee
  INNER JOIN Contact_Info
  ON Employee.EmpID = Contact_Info.EmpID;
  

  
  

  This result of the following code will be:

  EmpID	Name	Age	Salary	Address
  2	Marry	24	2750	XXX, Brooklyn, New York, USA
  3	Jo	27	2800	XXX, Grenelle, Paris, France
  4	Kim	30	3100	XXX, Geuzenveld, Amsterdam, Netherlands
  6	Huang	28	2800	XXX, Yizhuangzhen, Beijing, China