Joins the rows of {0} with the rows of {2} based on the equality of the values of the key columns selected by {1} (for {0}) ...

Joins the rows of {0} with the rows of {2} based on the equality of the values of the key columns selected by {1} (for {0}) and {3} (for {2}). The results are entered into the column named {4}.
This function behaves similarly to Table.Join with a JoinKind of LeftOuter except that the join results are presented in a nested rather than flattened fashion.