Text copied!
SQL inner join
INNER JOIN(or JOIN) returns only the matching rows between two tables. By default 'JOIN' keyword is treated as 'INNER JOIN'.
The syntax of the SQL inner join generally looks like this :
SELECT column_name(s) FROM table1 JOIN table2 ON table1.column_name = table2.column_name;
• 'table1' and 'table2' refer to the two tables being joined together.
• 'column_name(s)' refer to the selected columns from the tables being joined together.
• 'ON' clause is used to specify the conditions for joining two or more tables together.
As seen in above image, SQL inner join produces a result set that includes only the rows that exist in both 'Table-A' and 'Table-B'.
Here's an example of how you might use the SQL inner join :
Let's suppose we have two tables :
[a] Employees Table :
→ It contains columns [Employee_Id], [Employee_Name], [Gender] and [Department_Id].
[b] Departments Table :
→ It contains columns [Department_Id] and [Department_Name].
1. Let's use SQL inner join to retrieve the employees names and their respective department names by joining the [Employees] and [Departments] tables together based on matching values in both the tables.
2. Please run the following SQL statement :
SELECT Emp.Employee_Name, Emp.Department_Id, Dpt.Department_Name
FROM [Employees] Emp
INNER JOIN [Departments] Dpt
ON Emp.Department_Id = Dpt.Department_Id
3. Above statement selects the columns from both tables based on the matching values in the 'Department_Id' column and returns the resulting data as the output.
• As you have seen, Only specific selected columns ( [Employee_Name], [Department_Id] from "Employees" table and [Department_Name] from "Departments" table ) are returned.
• It returned only the rows where the [Department_Id] column has values of '1' or '2' because these are the only values that exist in both tables.
That's it! You have successfully retrieved data using 'INNER JOIN' statement.