The issue with combining IFNULL function

The exported file for the database is in the attachment.

--orignal sql

SELECT O_TOTALPRICE, O_ORDERKEY, O_CUSTKEY 

FROM ORDERS 

WHERE IFNULL(

    O_CUSTKEY, 

    IFNULL(O_ORDERKEY, IFNULL(0.21501538554113775, O_ORDERDATE))

) <= O_CLERK

GROUP BY O_TOTALPRICE, O_ORDERKEY, O_CUSTKEY;

return 1448 rows

--rewritten sql

SELECT distinct O_TOTALPRICE, O_ORDERKEY , O_CUSTKEY

FROM ORDERS 

WHERE (O_CUSTKEY <= O_CLERK OR 

      (O_CUSTKEY IS NULL AND O_ORDERKEY <= O_CLERK) );

reurn 0 row
These two queries are logically equivalent because they both filter based on the relationship between O_CUSTKEY and O_CLERK while handling potential NULL values.

In the original query, nested IFNULL functions are used to handle cases where O_CUSTKEY, O_ORDERKEY, O_ORDERDATE, or the constant 0.21501538554113775 may be NULL. If O_CUSTKEY is not NULL, the query checks O_CUSTKEY <= O_CLERK. If O_CUSTKEY is NULL, it moves on to evaluate O_ORDERKEY and other values.

In the rewritten query, the same logic is explicitly expressed using OR and AND. It first checks whether O_CUSTKEY <= O_CLERK. If O_CUSTKEY is NULL, it evaluates whether O_ORDERKEY <= O_CLERK.

The two SQL queries are logically equivalent, but they return different results, indicating the presence of a bug.