create table t1 (a int);

insert into t1 values (1),(2),(3);

SELECT a FROM t1 WHERE EXISTS ( SELECT count(*) over () FROM (select 1)dt WHERE  (EXISTS ( SELECT t1.a FROM (select 1)f WHERE 0 )) );

MariaDB [sqltester]> create table t1 (a int);

Query OK, 0 rows affected (0,031 sec)

MariaDB [sqltester]> insert into t1 values (1),(2),(3);

Query OK, 3 rows affected (0,002 sec)

Records: 3  Duplicates: 0  Warnings: 0

MariaDB [sqltester]> SELECT a FROM t1 WHERE EXISTS ( SELECT count(*) over () FROM (select 1)dt WHERE  (EXISTS ( SELECT t1.a FROM (select 1)f WHERE 0 )) );

+------+

| a    |

+------+

|    1 |

|    2 |

|    3 |

+------+

3 rows in set (0,002 sec)

MariaDB [sqltester]> SELECT count(*) over () FROM (select 1)dt where 0;

Empty set (0,000 sec)

MariaDB [sqltester]> explain extended SELECT a FROM t1 WHERE EXISTS ( SELECT count(*) over () FROM (select 1)dt WHERE  (EXISTS ( SELECT t1.a FROM (select 1)f WHERE 0 )) );

+------+--------------------+------------+--------+---------------+------+---------+------+------+----------+------------------+

| id   | select_type        | table      | type   | possible_keys | key  | key_len | ref  | rows | filtered | Extra            |

+------+--------------------+------------+--------+---------------+------+---------+------+------+----------+------------------+

|    1 | PRIMARY            | t1         | ALL    | NULL          | NULL | NULL    | NULL | 3    |   100.00 | Using where      |

|    2 | DEPENDENT SUBQUERY | <derived3> | system | NULL          | NULL | NULL    | NULL | 1    |   100.00 | Using temporary  |

|    4 | DEPENDENT SUBQUERY | NULL       | NULL   | NULL          | NULL | NULL    | NULL | NULL |     NULL | Impossible WHERE |

|    5 | DERIVED            | NULL       | NULL   | NULL          | NULL | NULL    | NULL | NULL |     NULL | No tables used   |

|    3 | DERIVED            | NULL       | NULL   | NULL          | NULL | NULL    | NULL | NULL |     NULL | No tables used   |

+------+--------------------+------------+--------+---------------+------+---------+------+------+----------+------------------+

5 rows in set, 2 warnings (0,001 sec)

Note (Code 1276): Field or reference 'sqltester.t1.a' of SELECT #4 was resolved in SELECT #1

Note (Code 1003): /* select#1 */ select `sqltester`.`t1`.`a` AS `a` from `sqltester`.`t1` where <in_optimizer>(1,<expr_cache><`sqltester`.`t1`.`a`>(exists(/* select#2 */ select count(0) over () from dual where <in_optimizer>(1,<expr_cache><`sqltester`.`t1`.`a`>(exists(/* select#4 */ select `sqltester`.`t1`.`a` from (/* select#5 */ select 1 AS `1`) `f` where 0 limit 1))) limit 1)))