Added toStartOfFifteenMinutes Function

Why it matters

This function was created to facilitate time-based data aggregation or grouping by 15-minute intervals. It solves the problem of manually calculating the start of each 15-minute period, simplifying queries that require partitioning timestamps into quarter-hour segments. This provides value by making time series analysis and reporting more straightforward and efficient.

How to use it

Use the toStartOfFifteenMinutes function by passing a datetime value as its argument. The function returns a DateTime value representing the beginning of the 15-minute interval that contains the input datetime.

Example:

SELECT toStartOfFifteenMinutes(datetime_column) AS interval_start
FROM table