Question 260
A data cleaner unexpectedly returns no eligible rows when excluding identifiers that can be NULL. How should the team validate the selected design?
Explanation
Correct Answer
NOT IN with unknown NULL comparison can filter unexpectedly; NOT EXISTS tests matching row presence. The observation “Valid nonmatching rows remain while genuinely matching identifiers are excluded” directly confirms the chosen action worked for this situation: A data cleaner unexpectedly returns no eligible rows when excluding identifiers that can be NULL.
Incorrect Answers
LAG reads a preceding row within a partition without a self-join for each row. This observation would not establish that the required result occurred for A data cleaner unexpectedly returns no eligible rows when excluding identifiers that can be NULL. The confirming test is: Valid nonmatching rows remain while genuinely matching identifiers are excluded.
OPENJSON exposes elements as rows and explicit schema maps document fields into SQL types. This observation would not establish that the required result occurred for A data cleaner unexpectedly returns no eligible rows when excluding identifiers that can be NULL. The confirming test is: Valid nonmatching rows remain while genuinely matching identifiers are excluded.
Set-based filtering and stable paging reduce unnecessary data movement; paging without deterministic order can skip or repeat rows. This observation would not establish that the required result occurred for A data cleaner unexpectedly returns no eligible rows when excluding identifiers that can be NULL. The confirming test is: Valid nonmatching rows remain while genuinely matching identifiers are excluded.