arrayJoin function

    Normal functions do not change a set of rows, but just change the values in each row (map).
    Aggregate functions compress a set of rows (fold or reduce).
    The ‘arrayJoin’ function takes each row and generates a set of rows (unfold).

    A query can use multiple functions. In this case, the transformation is performed multiple times.

    Example:

    1. ┌─dst─┬─\'Hello\'─┬─src─────┐
    2. │   2 │ Hello     │ [1,2,3] │
    3. └─────┴───────────┴─────────┘