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> Note that this SQL query is not very efficient. An experienced developer would rewrite it to use subqueries

Anyone care to explain why is that? I thought the query plan should be the same for JOINs and subqueries.

There is a difference in how large a set `array_agg` would need to process, since `LEFT JOIN` may produce a very sparse relation and NULLs still have to be scanned over.

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