Скачать или смотреть Querying with Recursive | Spot the Bad SQL Query Part 5

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This is part of the Spot the Bad SQL Query series.

Can you spot what's bad about this SQL query?

Join us on a code review journey, designed to help you identify common pitfalls, edge-cases, and anti-patterns when analyzing data using SQL. These mistakes will transcend simple typos, syntax errors, or historical quirks of SQL, and instead point to deeper conceptual and knowledge gaps when designing efficient, effective, correct queries.

In this series, we will review some bad SQL queries with the intention to systmetically improve it and to improve our use of this fundamental tool.

We'll see queries that…

are subtly wrong as a consequence of issues relating to null values
need to be slightly rewritten to make better use of SQL window functions
contain serious performance issues when using keywords like limit and offset
contain serious correctness issues when using (recursive) common-table expressions
don't correctly handle duplicates when performing set operations combining queries