summarize operator

Produces a table that aggregates the content of the input table.

Syntax

T | summarize [ SummarizeParameters ] [[Column =] Aggregation [, ...]] [by [Column =] GroupExpression [, ...]]

Parameters

[!NOTE] When the input table is empty, the output depends on whether GroupExpression is used:

• If GroupExpression is not provided, the output will be a single (empty) row.
• If GroupExpression is provided, the output will have no rows.

Returns

The input rows are arranged into groups having the same values of the by expressions. Then the specified aggregation functions are computed over each group, producing a row for each group. The result contains the by columns and also at least one column for each computed aggregate. (Some aggregation functions return multiple columns.)

The result has as many rows as there are distinct combinations of by values (which may be zero). If there are no group keys provided, the result has a single record.

To summarize over ranges of numeric values, use bin() to reduce ranges to discrete values.

Aggregates default values

The following table summarizes the default values of aggregations:

When using these aggregates over entities that includes null values, the null values will be ignored and won't participate in the calculation (see examples below).

Examples

Unique combination

The following query determines what unique combinations of State and EventType there are for storms that resulted in direct injury. There are no aggregation functions, just group-by keys. The output will just show the columns for those results.

StormEvents
| where InjuriesDirect > 0
| summarize by State, EventType

Output

The following table shows only the first 5 rows. To see the full output, run the query.

Minimum and maximum timestamp

Finds the minimum and maximum heavy rain storms in Hawaii. There's no group-by clause, so there's just one row in the output.

StormEvents
| where State == "HAWAII" and EventType == "Heavy Rain"
| project Duration = EndTime - StartTime
| summarize Min = min(Duration), Max = max(Duration)

Output

Distinct count

Create a row for each continent, showing a count of the cities in which activities occur. Because there are few values for "continent", no grouping function is needed in the 'by' clause:

[!div class="nextstepaction"] Run the query

StormEvents
| summarize TypesOfStorms=dcount(EventType) by State
| sort by TypesOfStorms

Output

The following table shows only the first 5 rows. To see the full output, run the query.

Histogram

The following example calculates a histogram storm event types that had storms lasting longer than 1 day. Because Duration has many values, use bin() to group its values into 1-day intervals.

[!div class="nextstepaction"] Run the query

StormEvents
| project EventType, Duration = EndTime - StartTime
| where Duration > 1d
| summarize EventCount=count() by EventType, Length=bin(Duration, 1d)
| sort by Length

Output