Joining Three Tables in Oracle

Disclaimer/Disclosure: Some of the content was synthetically produced using various Generative AI (artificial intelligence) tools; so, there may be inaccuracies or misleading information present in the video. Please consider this before relying on the content to make any decisions or take any actions etc. If you still have any concerns, please feel free to write them in a comment. Thank you.
---

Summary: Learn how to join three tables in Oracle to query and combine data effectively. This guide covers different types of joins and examples to help you master joining tables in Oracle.
---

When working with databases, you often need to combine data from multiple tables to get a comprehensive view of your data. Oracle, a powerful relational database management system, provides various join operations to enable you to efficiently combine data from different tables. In this guide, we will focus on how to join three tables in Oracle using different types of joins.

Types of Joins in Oracle

Before diving into how to join three tables, let's briefly review the different types of joins available in Oracle:

Inner Join: Combines rows from multiple tables based on a matching condition. Only rows that match the condition in all tables are included in the result.

Outer Join: Combines rows from multiple tables even if there is no match in one or more tables. There are three types of outer joins:

Left Outer Join: Includes all rows from the left table and matching rows from the right table. If there's no match, the result will include rows from the left table with nulls for columns from the right table.

Right Outer Join: Includes all rows from the right table and matching rows from the left table. If there's no match, the result will include rows from the right table with nulls for columns from the left table.

Full Outer Join: Combines rows from both tables, including rows that don't have matches in the other table.

Cross Join: Produces a Cartesian product of the tables, resulting in all possible combinations of rows.

Self Join: Joins a table to itself, typically using an alias to distinguish the instances of the table.

Joining Three Tables in Oracle

Joining three tables in Oracle follows similar principles as joining two tables, with the additional complexity of combining data from three sources. You can use various types of joins (inner, outer, or cross joins) depending on your needs. Let's explore how to join three tables using these joins.

Inner Join

In an inner join, the result will include rows from all three tables where there is a match in the specified columns. Here's an example query to join three tables:

[[See Video to Reveal this Text or Code Snippet]]

In this example, the query selects columns from table1, table2, and table3, joining them based on matching common_column and another_common_column.

Left Outer Join

In a left outer join, the result will include all rows from the left table(s) even if there is no match in the right table(s). Here's an example:

[[See Video to Reveal this Text or Code Snippet]]

In this case, the query retrieves all rows from table1 and table2 that match on common_column, and all rows from table1 and table3 that match on common_column, including rows from table1 that may not have matches in either table2 or table3.

Right Outer Join

In a right outer join, the result will include all rows from the right table(s) even if there is no match in the left table(s). Here's an example:

[[See Video to Reveal this Text or Code Snippet]]

In this query, the join prioritizes including all rows from table2 and table3, even if there are no matches in table1.

Conclusion

Joining three tables in Oracle is a powerful way to combine data from different sources. By using different types of joins (inner, outer, and cross), you can manipulate and query your data to meet your specific needs. By mastering these operations, you'll be well-equipped to handle complex queries and gain deeper insights from your data.