extend operator

Creates calculated columns and append them to the result set.

Syntax

T | extend [ColumnName | (ColumnName[, …]) =] Expression [, …]

Parameters

• If ColumnName is omitted, the output column name of Expression is automatically generated.
• If Expression returns more than one column, a list of column names can be specified in parentheses. Then, Expression’s output columns is given the specified names. If a list of the column names isn’t specified, all Expression’s output columns with generated names are added to the output.

Returns

A copy of the input tabular result set, such that:

1. Column names noted by extend that already exist in the input are removed and appended as their new calculated values.
2. Column names noted by extend that don’t exist in the input are appended as their new calculated values.

not have an index. In most cases, if the new column is set to be exactly the same as an existing table column that has an index, Kusto can automatically use the existing index. However, in some complex scenarios this propagation is not done. In such cases, if the goal is to rename a column, use the project-rename operator instead.

Example

StormEvents
| project EndTime, StartTime
| extend Duration = EndTime - StartTime

The following table shows only the first 10 results. To see the full output, run the query.

Related content

• Use series_stats to return multiple columns