Issues with Subquery Independence

The exported file for the database is in the attachment.

--orignal sql

SELECT L_SHIPINSTRUCT, L_EXTENDEDPRICE, L_COMMENT

FROM LINEITEM

WHERE L_SHIPMODE NOT IN (

    SELECT L_COMMITDATE

    FROM LINEITEM

);

return 0 row

--rewritten sql

SELECT L_SHIPINSTRUCT, L_EXTENDEDPRICE, L_COMMENT

FROM LINEITEM

WHERE L_SHIPMODE NOT IN (

    SELECT L_COMMITDATE

    FROM LINEITEM

    WHERE L_COMMITDATE IS NOT NULL

);

return 5905 rows

The two queries are identical, although the rewritten query includes an additional WHERE L_COMMITDATE IS NOT NULL condition in the subquery. Since NULL values are implicitly excluded in the original query, this condition does not have a substantial impact on the final result. However, the different row counts indicate that a bug is present.