Temporary Tables in SQL

SQL, one of the most popular relational database management systems, offers a wide range of features to enhance data manipulation and analysis. One such feature is the use of temporary tables.

Temporary tables provide a way to store and manipulate intermediate result sets within a session, offering flexibility and performance gains. In this article, we’ll dive into the world of temporary tables and explore their benefits and practical use cases in SQL.

1. Understanding Temporary Tables

Temporary tables, as the name suggests, are tables that exist temporarily and are tied to a specific session. They are useful for storing intermediate results or working with complex data manipulations. Temporary tables are stored in the MySQL temporary directory and have a unique name that is automatically generated by the system. They are only visible and accessible within the session that creates them, and they are automatically dropped when the session ends.

2. Creating Temporary Tables

Creating a temporary table in MySQL is straightforward. Let’s consider an example where we want to store the below data in a temporary table:

-- I'd like to show this query's result as a temporary table.
-- (It shows book's titles and publisher's country.)

SELECT title, country
FROM titles
LEFT JOIN publishers
USING (pub_id)

-- Let's create a temporary table as 'titles_publishers'.

CREATE TEMPORARY TABLE titles_publishers
SELECT title, country
FROM titles
LEFT JOIN publishers
USING (pub_id);

-- Let's retrieve all the data from the temporary table 'titles_publishers'.

SELECT *
FROM titles_publishers;

3. Using Temporary Tables

-- Display book's titles and publisher's country where title starts with 'The'.

SELECT *
FROM titles_publishers
WHERE title LIKE 'The%';

4. Joining Temporary Tables with Regular Tables

One of the powerful aspects of temporary tables is the ability to join them with regular tables. This allows us to combine temporary data with existing data for complex queries. Consider the following example:

-- Display book's titles and publisher's country where title starts with 'The'.

SELECT titles_publishers.title, titles.price
FROM titles_publishers
LEFT JOIN titles
ON titles_publishers.title = titles.title;

5. Dropping Temporary Tables

Temporary tables are automatically dropped when the session ends, but we can also explicitly drop them before that if needed. To drop a temporary table, we can use the DROP TABLE statement:

DROP TABLE titles_publishers;

Conclusion

Temporary tables in MySQL offer a powerful and versatile solution for storing and manipulating intermediate result sets. They enhance performance and flexibility in data manipulation tasks.

With temporary tables, you can boost your data manipulation capabilities and achieve more efficient and effective data analysis in MySQL.

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