MariaDB [test]> explain extended select v2.b AS f from v v1 left join v v2 ON (false) having (f = f);
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+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------------------------------------------+
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
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+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------------------------------------------+
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| 1 | SIMPLE | t | ALL | NULL | NULL | NULL | NULL | 2 | 100.00 | |
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| 1 | SIMPLE | t | ALL | NULL | NULL | NULL | NULL | 2 | 100.00 | Using where; Using join buffer (flat, BNL join) |
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+------+-------------+-------+------+---------------+------+---------+------+------+----------+-------------------------------------------------+
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2 rows in set, 1 warning (0.001 sec)
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MariaDB [test]> show warnings;
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+-------+------+--------------------------------------------------------------------------------------------------------------------+
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| Level | Code | Message |
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+-------+------+--------------------------------------------------------------------------------------------------------------------+
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| Note | 1003 | select if(`test`.`t`.`a` = 1,'Y','N') AS `f` from `test`.`t` left join (`test`.`t`) on(0) where 1 having `b` = `b` |
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+-------+------+--------------------------------------------------------------------------------------------------------------------+
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1 row in set (0.000 sec)
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