SQL INNER JOIN

The SQL INNER JOIN returns the records (or rows) present in both tables, If there is at least one match between columns. Or we can Simply say, INNER JOIN returns the records (or rows) present in both tables as long as the Condition after the ON Keyword is TRUE.

SQL INNER JOIN Syntax

The basic syntax of the Inner Join in SQL Server 2014 is as shown below:

In SQL, Inner join is the default join so it is optional to use the INNER Keyword. Let us see the visual representation of the Inner join for better understanding.

From the above image you can understand easily that, Inner join only displays the matching records from Table 1 and Table 2 (Like an Intersect in Math)

In this article we will show you, How to write Inner Join in SQL Server 2014. For this, We are going to use two tables (Employee and Department) present in our [SQL Server Tutorials] Database.

Data present in the Employee Table is:

Data present in the Department Table is:

SQL Inner Join – Selecting All Columns

The following SQL Query will display all the columns present in Employees and Department tables

T-SQL CODE

OUTPUT

If you observe the above screenshot, Although we have 15 records in Employee table, Inner join is displaying 11 records. This is because, Department Id for the remaining 4 records (i., ID number 10, 11, 14 and 15) in Employee table are NULLS.

NOTE: The [Department ID] column is repeated twice, which is annoying to the user. By selecting individual column names we can avoid unwanted columns so, Please avoid SELECT * Statements in INNER JOINS

SQL Inner Join – Selecting Few Columns

Please place the required columns after the SELECT Statement to avoid unwanted columns

T-SQL CODE

OUTPUT

Above query will perfectly work as long as the column names from both tables (Employee and Department) are different like above. What happens if we have same Column names in both the tables? Well, you will end up in a mess. Let us see how to resolve the issue.

The following query is using table name before the column name and also used the SQL ALIAS names to rename the column names. By this approach we can inform the Database that we are looking for columns belonging to particular table.

T-SQL CODE

OUTPUT

Although we don’t have any common column names, Imagine we have [DepartmentName] column in Employee as well and we want to display Department Columns in both the tables.

We can simply write as

NOTE: It is always best practice to use the table name before the Column name in Joins. For example, SELECT Employee.Firstname

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