Total Column Usage Count

column_usage.kql

AzureDiagnostics
| where OperationName == "QueryEnd"
| where EventSubclass_s == 3
| where Resource == "ENTERAZURERESOURCE" //Enter Azure Resource
| where ApplicationName_s == "PowerBI"
| where TimeGenerated > ago(30d) //Remove if you would prefer to use the time selection in Azure
| extend extract_column = extract_all(@"('.*?'\[.*?\])",TextData_s)
| mv-expand extract_column
| summarize Total_Number_Queried=dcount(SPID_s) by Table_Column= tostring(extract_column)