Bug #117704 WHERE Clause Fails to Filter NULL Values in Condition (col1 = col2)

Description:
When using a WHERE clause with a condition like (col1 =  col2), MySQL fails to filter the rows correctly. 
Specifically, when performing a RIGHT OUTER JOIN and checking the condition (ref_1.c1) = (subq_0.c_0) where subq_0.c_0 is NULL, the result should be filtered out because NULL = ref_1.c1 should evaluate to NULL, and therefore not return rows.However, MySQL does not filter out rows as expected.

How to repeat:
Create Test Table and Insert Sample Data:
DROP TABLE IF EXISTS `t1`;
CREATE TABLE `t1` (
  `c1` int
) ;

INSERT INTO `t1` VALUES (1);

Execute the Following Query:
select  
  subq_0.c_0 as c_0, 
  ref_1.c1 as c_1
from 
  ((select  
          1 as c_0

mysql version:
github commit: 61a3a1d8ef15512396b4c2af46e922a19bf2b174
version: 9.1.0 

os version:
Linux ubuntu 5.15.0-134-generic #145~20.04.1-Ubuntu SMP Mon Feb 17 13:27:16 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
        from 
          t1 as ref_0
        where false) as subq_0
    right outer join t1 as ref_1
    on (true))
where 
   ((ref_1.c1) = (subq_0.c_0));

Expected Result:
Empty set (0.00 sec)

Actual Result:
+-----+------+
| c_0 | c_1  |
+-----+------+
| NULL |    1 |
+-----+------+
1 row in set (0.01 sec)

Here, NULL = 1 should evaluate to NULL, and thus the row should be filtered out. However, it still appears in the result.

Hello zhiqiang cheng,

Thank you for the report and test case.

regards,
Umesh