Results of IFNULL(NULL,LAST_VALUE(a) OVER ()) are non-deterministic;

CREATE TABLE t(a INT, b INT);

INSERT INTO t VALUES (100,1), (200,1),(300,2),(400,2),(500,3),(600,3);

SELECT IFNULL(NULL,LAST_VALUE(a) OVER ()) from t;

MariaDB [test]> SELECT IFNULL(NULL,LAST_VALUE(a) OVER ()) from t;

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

| IFNULL(NULL,LAST_VALUE(a) OVER ()) |

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

|                                600 |

|                                600 |

|                                600 |

|                                600 |

|                                600 |

|                                600 |

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

6 rows in set (0.00 sec)

MariaDB [test]> SELECT IFNULL(NULL,LAST_VALUE(a) OVER ()) from t;

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

| IFNULL(NULL,LAST_VALUE(a) OVER ()) |

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

|                                100 |

|                                100 |

|                                100 |

|                                100 |

|                                100 |

|                                100 |

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

6 rows in set (0.00 sec)

MariaDB [test]> SELECT IFNULL(NULL,LAST_VALUE(a) OVER ()) from t;

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

| IFNULL(NULL,LAST_VALUE(a) OVER ()) |

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

|                                200 |

|                                200 |

|                                200 |

|                                200 |

|                                200 |

|                                200 |

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

6 rows in set (0.00 sec)