This function returns the mode of the values in each group, the most frequently occurring value or values in each group. If multiple values have the same maximum number of occurrences, multiple values are returned. When dragging a Mode element into a variable, the following tree element is created.
Variable Creation > Input > Variables: SQL Elements pane - Aggregation > Time Series > Mode
A Column or other non-aggregate expression can be moved over the (empty-Value Expression) branch of the tree.