KQL – Extend

Allows to add calculated column to your result set

//adds a calculated column to the result set
Perf
| where CounterName == "Free Megabytes"
|extend FreeGB = CounterValue / 1000

//create multiple columns at the same time
Perf
| where CounterName == "Free Megabytes"
|extend FreeGB = CounterValue / 1000
, FreeKB = CounterValue * 1000

//repeat a column
Perf
| where CounterName == "Free Megabytes"
|extend FreeGB = CounterValue / 1000
, FreeMB = CounterValue
, FreeKB = CounterValue * 1000

//create new string in column
Perf
| where TimeGenerated >=ago(10m)
| extend ObjectCounter = strcat(ObjectName, " - ", CounterName)