SQL INNER JOIN

 An INNER JOIN in SQL is used to retrieve rows from two or more tables that meet a specific condition. It only includes rows where there is a match in both tables based on the join condition.

Syntax:

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

Explanation:

• table1 and table2: The tables you are joining.
• ON: Specifies the condition that links the tables (usually a column common to both tables, such as a foreign key relationship).

Example:

Tables:

Employees

EmployeeID	Name	DepartmentID
1	Alice	101
2	Bob	102
3	Charlie	NULL

Departments

DepartmentID	DepartmentName
101	HR
102	IT
103	Sales

Query:

SELECT Employees.Name, Departments.DepartmentName
FROM Employees
INNER JOIN Departments
ON Employees.DepartmentID = Departments.DepartmentID;

Result:

Name	DepartmentName
Alice	HR
Bob	IT

Key Points:

1. Only Matching Rows: Rows are returned only if there is a match between table1 and table2 based on the ON condition.
2. No Null Matches: Rows with NULL values in the columns used for the join condition are excluded.
3. Alias Usage: You can use table aliases to make the query more readable:

   SELECT e.Name, d.DepartmentName
   FROM Employees e
   INNER JOIN Departments d
   ON e.DepartmentID = d.DepartmentID;