A Join is any operation performed on database tables to collect data from related tables according to common fields or columns. You will come across two major types of joins in SQL: inner join and outer join. Dig into this article to learn more about inner join in SQL.
The inner join in SQL is useful for combining records from two related tables according to common columns. The inner join query can compare every row of the first table with every row of the second table to identify all pairs of rows that meet the join predicate. When the join-predicate is met, the column value of every matched row pair of both tables is combined into an outcome row.
According to SQL inner join meaning, it is the default join in SQL. Even if “Join” is used instead of “Inner Join,” tables will get joined according to matching records of common columns. The inner join in SQL is also frequently used and called the Equijoin.
The biggest difference between an outer join and an inner join in SQL is that the inner join only keeps information from both tables related to one another. But the outer join will also keep information unrelated to the other table in the resulting table.
Let us consider a hypothetical example to understand SQL inner join in action. Let us begin with a list of pizza joints in different cities.
Company ID | Company Name | Company City |
---|---|---|
1 | Pizza Hut | San Francisco |
2 | Domino’s | Los Angeles |
3 | Papa John’s | San Diego |
4 | Chuck e Cheese | Chicago |
5 | Nino Pizza | Las Vegas |
Now let’s talk about the food items sold by each joint and the number of units sold.
Item ID | Item Name | Units Sold | Company ID |
---|---|---|---|
1 | Medium Pizza | 5 | 2 |
2 | Small Pizza | 11 | 5 |
3 | Garlic Knots | 7 | 3 |
4 | Breadsticks | 8 | 4 |
5 | Medium Pizza | 4 | 1 |
You will be able to combine the two tables by using the inner join query. It will ensure that you can view the items and number of units delivered by pizza outlets in different cities.
The inner join syntax in SQL is as follows:
ON tableA.id_field = tableB.id_field;
The join condition for any natural join is an equijoin of all columns with the same name. The ON clause is used to mention arbitrary conditions or particular columns to join. The inner join in SQL condition is distinguished from other search conditions.
The ON clause makes it easy to comprehend code. The ON clause is useful for joining columns with different names. It enables specifying join conditions different from any search or filter conditions in the WHERE clause.
Now, let’s consider the two tables from the inner join in SQL in action example. With that, we are going to add some more data related to water parks. Let us consider the number of pizzas sold at several water parks from different outlets. Using an SQL inner join query, you will be able to combine the data from all three tables and acquire several valuable insights.
Some real-world examples of inner join SQL are as follows:
You can use an inner join in SQL query to calculate total product sales. Apart from that, you will be able to display the top products by sale and the products with the lowest production cost. Moreover, you will be able to determine the sales across different product categories.
Let us reveal the code for displaying sales products by figures:
Suppose you want to find the monthly salary of employees from a table where the annual salary is present. You will have to divide the annual salary by 12 and create an alias column as Monthly salary to find out the monthly salary of each employee. You will have to use the following inner SQL join query for it:
Some of the best practices for using inner join SQL are as follows:
Some tips for optimizing inner join queries in SQL are as follows:
Instead of using SELECT *, try specifying the columns in the select clause. The unnecessary column spaces add extra load to the database. It slows down the whole system along with the single SQL.
Check out: SQL Interview Questions
Some common mistakes to avoid while using inner join in SQL are as follows:
Poor formatting is another inner join query mistake. The right formatting is necessary for improved readability of your inner join query. You need to focus more on formatting when you have complex joins with multiple conditions and tables.
The inner join in SQL enables you to query data from two or more related tables. It is the most commonly used join in SQL. Learn about inner SQL joins in detail to apply it in real-life scenarios.
Book a free counselling session
Get a personalized career roadmap
Get tailored program recommendations
Explore industry trends and job opportunities
Programs tailored for your Success
Popular
Data Science
Technology
Finance
Management
Future Tech
© 2024 Hero Vired. All rights reserved