Kusto query remove double entries

Question

I have a query that returns several entries with timestamp and an operation_Id. Entry 2 and 3 have the same operation_Id but different timestamps. How can I remove the duplicate operation_Id, the first shall be used - and I still want to display the timestamp.

timestamp	operation_Id	name
2022-10-28T06:13:05.789Z	12d83416-0c94-4c98-9523-603b7e634a14	iOS
2022-10-28T03:50:44.249Z	642bb5d7-69e5-437a-b086-d89eec93438b	iOS
2022-10-28T03:50:42.662Z	642bb5d7-69e5-437a-b086-d89eec93438b	iOS

I know I can use "distinct".

| distinct operation_Id, OS;

operation_Id	name
12d83416-0c94-4c98-9523-603b7e634a14	iOS
642bb5d7-69e5-437a-b086-d89eec93438b	iOS
642bb5d7-69e5-437a-b086-d89eec93438b	iOS

But how do I add now the timestamp?

I cannot do something like this, because then I am back to my first problem :-)

| distinct timestamp, operation_Id, OS;

I also tried with "summarize" but it summarized all operation_Id, even the operation_Id was different

Answer 1

arg_min()

datatable(timestamp:datetime, operation_Id:string, name:string)
[
    datetime(2022-10-28T06:13:05.789Z) ,"12d83416-0c94-4c98-9523-603b7e634a14" ,"iOS"
   ,datetime(2022-10-28T03:50:44.249Z) ,"642bb5d7-69e5-437a-b086-d89eec93438b" ,"iOS"
   ,datetime(2022-10-28T03:50:42.662Z) ,"642bb5d7-69e5-437a-b086-d89eec93438b" ,"iOS"
]
| summarize arg_min(timestamp, *) by operation_Id

operation_Id	timestamp	name
642bb5d7-69e5-437a-b086-d89eec93438b	2022-10-28T03:50:42.662Z	iOS
12d83416-0c94-4c98-9523-603b7e634a14	2022-10-28T06:13:05.789Z	iOS

Fiddle