Issues with the COALESCE function.

*The exported file for the database is in the attachment.

--orignal sql

SELECT ALL LINEITEM.L_SHIPMODE AS REF0, LINEITEM.L_TAX AS REF1 

FROM LINEITEM 

WHERE (LINEITEM.L_SHIPINSTRUCT) > 

      100

GROUP BY LINEITEM.L_SHIPMODE, LINEITEM.L_TAX;

return 0 rows

--rewritten sql 

SELECT ALL LINEITEM.L_SHIPMODE AS REF0, LINEITEM.L_TAX AS REF1 

FROM LINEITEM

WHERE (LINEITEM.L_SHIPINSTRUCT) > 

      COALESCE(100, LINEITEM.L_DISCOUNT, LINEITEM.L_COMMITDATE)

GROUP BY LINEITEM.L_SHIPMODE, LINEITEM.L_TAX;

return 72 row

These two queries are logically equivalent, though they use different syntax to handle the comparison value.

In the original query, LINEITEM.L_SHIPINSTRUCT is compared to the constant 100, filtering rows where LINEITEM.L_SHIPINSTRUCT is greater than 100.

In the rewritten query, the COALESCE(100, LINEITEM.L_DISCOUNT, LINEITEM.L_COMMITDATE) function is used to select the first non-NULL value from 100, LINEITEM.L_DISCOUNT, and LINEITEM.L_COMMITDATE. This value is then compared with LINEITEM.L_SHIPINSTRUCT. And the result of COALESCE is still 100.

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