【Bug】SQL NOT working correctly when using same alias name in the main query and subquery

[hiroyuki0415]

SELECT s.fullname,
       b_s.fullname
FROM   businessunit AS b
       INNER JOIN
       systemuser AS s
       ON b.businessunitid = s.businessunitid
          AND s.fullname LIKE 'AAA%'
       INNER JOIN
       (SELECT b.businessunitid,
               s.fullname,
               s.systemuserid
        FROM   businessunit AS b
               INNER JOIN
               systemuser AS s
               ON b.businessunitid = s.businessunitid
        WHERE  s.fullname LIKE 'XXX%') AS b_s
       ON s.systemuserid = b_s.systemuserid;

The result of this SQL should be empty, but it's not.

• It works correctly if you use different alias names for the main query and subquery.
• I get the below error If I remove b.businessunitid in the subquery:

  Sequence contains more than one matching element

Thanks in advance for your support.