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SQL RIGHT JOIN
Starting here? This lesson is part of a full-length tutorial in using SQL for Data Analysis. Check out the beginning.
The RIGHT JOIN command
Right joins are similar to left joins except they return all rows from the table in the RIGHT JOIN clause and only matching rows from the table in the FROM clause.
RIGHT JOIN is rarely used because you can achieve the results of a RIGHT JOIN by simply switching the two joined table names in a LEFT JOIN. For example, in this query of the Crunchbase dataset, the LEFT JOIN section:
SELECT companies.permalink AS companies_permalink,
companies.name AS companies_name,
acquisitions.company_permalink AS acquisitions_permalink,
acquisitions.acquired_at AS acquired_date
FROM tutorial.crunchbase_companies companies
LEFT JOIN tutorial.crunchbase_acquisitions acquisitions
ON companies.permalink = acquisitions.company_permalink
produces the same results as this query:
SELECT companies.permalink AS companies_permalink,
companies.name AS companies_name,
acquisitions.company_permalink AS acquisitions_permalink,
acquisitions.acquired_at AS acquired_date
FROM tutorial.crunchbase_acquisitions acquisitions
RIGHT JOIN tutorial.crunchbase_companies companies
ON companies.permalink = acquisitions.company_permalink
The convention of always using LEFT JOIN probably exists to make queries easier to read and audit, but beyond that there isn’t necessarily a strong reason to avoid using RIGHT JOIN.
It’s worth noting that LEFT JOIN and RIGHT JOIN can be written as LEFT OUTER JOIN and RIGHT OUTER JOIN, respectively.
Sharpen your SQL skills
RIGHT JOIN instead of a LEFT JOIN. The goal is to produce the exact same results.