SQL Server Inner Join

Introduction

SQL Server Inner Join is a type of join operation used in SQL Server to combine data from two or more tables based on a common column or set of columns.

The Inner Join operation in SQL Server returns only the rows that have matching values in both the tables being joined. In other words, Inner Join returns the intersection of the two tables.

Syntax

The basic syntax for Inner Join in SQL Server is as follows:

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

In this syntax, table1 and table2 are the names of the tables being joined. column_name is the name of the column(s) that both tables share. The ON keyword specifies the condition for the join operation.

Example

Assume we have two tables, employees and departments, as follows:

Employees Table

| EmployeeID | EmployeeName | DepartmentID | |------------|--------------|--------------| | 1 | John Smith | 1 | | 2 | Jane Doe | 2 | | 3 | Bob Johnson | 1 | | 4 | Emily Brown | 3 |

Departments Table

| DepartmentID | DepartmentName | |--------------|----------------| | 1 | Sales | | 2 | Marketing | | 3 | Finance |

To join these two tables on the DepartmentID column, we can use the following SQL query:

SELECT employees.EmployeeName, departments.DepartmentName
FROM employees
INNER JOIN departments ON employees.DepartmentID = departments.DepartmentID;

This query will return the following results:

| EmployeeName | DepartmentName | |--------------|----------------| | John Smith | Sales | | Jane Doe | Marketing | | Bob Johnson | Sales | | Emily Brown | Finance |

Conclusion

Inner Join is a powerful tool in SQL Server that allows us to combine data from multiple tables based on a common column. By using Inner Join, we can easily retrieve the data we need to support our business operations.