When can NOT IN return zero rows unexpectedly?

Problem Statement

Explanation

NOT IN compares each value to the list. If the list contains NULL, comparisons become unknown and no row qualifies. Use NOT EXISTS for anti-joins, or ensure the subquery column is declared NOT NULL or filtered to exclude NULL.

Code Solution

SolutionRead Only

SELECT a.id
FROM A a
WHERE a.id NOT IN (
  SELECT b.a_id FROM B b WHERE b.a_id IS NOT NULL
);

Practice Sets

This question appears in the following practice sets:

Subqueries & CTEs (incl. Recursive)

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When can NOT IN return zero rows unexpectedly?

Problem Statement

Explanation

Code Solution

Practice Sets

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Master Interviews Anywhere, Anytime

When can NOT IN return zero rows unexpectedly?

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