WITH cte AS (SELECT 1) SELECT * from cte; # returns error if database is not selected

USE test;

WITH cte AS (SELECT 1 AS a) SELECT test.cte.a FROM test.cte; #works, even if database test does not exist

CREATE DATABASE test;

USE test;

WITH cte AS (SELECT 1 AS a) SELECT test.cte.a FROM test.cte; # works

SELECT test.d1.a FROM (SELECT 1 AS a) d1;		# error, derived table does not belong to database test;

SELECT d1.a FROM (SELECT 1 AS a) d1;	# works

MariaDB [(none)]> WITH cte AS (SELECT 1) SELECT * from cte;

ERROR 1046 (3D000): No database selected

MariaDB [(none)]> USE test;

ERROR 1049 (42000): Unknown database 'test'

MariaDB [(none)]> WITH cte AS (SELECT 1 AS a) SELECT test.cte.a FROM test.cte;

+---+

| a |

+---+

| 1 |

+---+

1 row in set (0.00 sec)

MariaDB [(none)]> CREATE DATABASE test;

Query OK, 1 row affected (0.00 sec)

MariaDB [(none)]> USE test;

Database changed

MariaDB [test]> WITH cte AS (SELECT 1 AS a) SELECT test.cte.a FROM test.cte; 

+---+

| a |

+---+

| 1 |

+---+

1 row in set (0.00 sec)

MariaDB [test]> SELECT test.d1.a FROM (SELECT 1 AS a) d1;

ERROR 1054 (42S22): Unknown column 'test.d1.a' in 'field list'

MariaDB [test]> SELECT d1.a FROM (SELECT 1 AS a) d1;

+---+

| a |

+---+

| 1 |

+---+

1 row in set (0.00 sec)