kunHøyreLeftJoin

                venstre høyre  kunHøyreLeftJoin
    2020-01-01  +---+
                | x |
    2020-01-02  |   |   +---+  +------------+
                |   |   | 1 |  | 1          |
    2020-01-03  +---+   |   |  +------------+
                        |   |
    2020-01-04          +---+

    2020-01-05  +---+
                | y |
    2020-01-06  +---+