Your engine lacks FULL OUTER JOIN. How can you emulate it, and what are the trade-offs?

Problem Statement

Explanation

Union a LEFT JOIN and a RIGHT JOIN, and remove the overlap by filtering the right side of one branch to NULL. This yields all matches and non-matches from both inputs. The trade-off is extra scan work and potential duplication risk if the filters are not precise. Indexes on join keys help both branches. Test the plan size on large tables to ensure it remains acceptable.

Code Solution

SolutionRead Only

SELECT a.*, b.*
FROM A a LEFT JOIN B b ON b.k = a.k
UNION ALL
SELECT a.*, b.*
FROM A a RIGHT JOIN B b ON b.k = a.k
WHERE a.k IS NULL;

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Your engine lacks FULL OUTER JOIN. How can you emulate it, and what are the trade-offs?

Problem Statement

Explanation

Code Solution

Practice Sets

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Master Interviews Anywhere, Anytime

Your engine lacks FULL OUTER JOIN. How can you emulate it, and what are the trade-offs?

Problem Statement

Explanation

Code Solution

Practice Sets

Related Questions

Which SQL statement retrieves all columns and rows from a table named employees?

Which clause filters rows before aggregation and affects which rows are grouped?

What is the default sort order when ORDER BY is used without ASC or DESC?

Which construct is commonly used to paginate results in SQL engines like Postgres and MySQL?

Which predicate correctly checks for missing values in standard SQL?

More from SQL & Databases

Master Interviews
Anywhere, Anytime