Comprehensive Detailed Explanation

Step 1: Understanding the requirement

We need a KQL query that:

Reads data from Weatherdata.

Orders by Datetime.

Calculates Delta_temperature as the difference between the current row and the preceding row.

Returns the final columns: Datetime, Lat, Long, Temperature, Delta_temperature.

Step 2: Evaluate the provided statements

Weatherdata → Starts the query with the source table.

| sort by Datetime asc → Ensures chronological order, required for prev() to work correctly.

| extend Delta_temperature = Temperature - prev(Temperature) → Computes difference between the current row and the previous row’s temperature.

| project Datetime, Lat, Long, Temperature, Delta_temperature → Selects the required output columns.

Step 3: Incorrect choices (to avoid)

next(Temperature,1) → Would calculate the difference with the next row, not the previous.

prev(Temperature,2) → Would skip one row, giving the difference with two rows back, which is not needed.

summarize … by Datetime → Aggregates the data; not required here since we just need row-level differences.

Step 4: Final Correct Sequence

Weatherdata

| sort by Datetime asc

| extend Delta_temperature = Temperature - prev(Temperature)

| project Datetime, Lat, Long, Temperature, Delta_temperature

References

prev() function in KQL

extend operator in KQL

project operator in KQL