Kusto / KQL query to take distinct output and then use in subsequent query

Question

I have the following data in a customMetrics table:

| date       | customDimension  | Type         | value |
| -----------------------------------------------------|
| 01-03-2021 | {"customer":"a"} | Transactions | 12    |
| 01-03-2021 | {"customer":"a"} | Value        | 784   |
| 01-03-2021 | {"customer":"c"} | Transactions | 733   |
| 01-03-2021 | {"customer":"b"} | Transactions | 7     |
| 01-03-2021 | {"customer":"c"} | Value        | 5     |
| 01-03-2021 | {"customer":"b"} | Value        | 85    |
| 01-03-2021 | {"customer":"a"} | Transactions | 50    |
| 01-03-2021 | {"customer":"a"} | Value        | 73    |
| 01-03-2021 | {"customer":"c"} | Value        | 3     |
| 01-03-2021 | {"customer":"a"} | Transactions | 13    |
| 01-03-2021 | {"customer":"a"} | Value        | 237   |
| 01-03-2021 | {"customer":"c"} | Transactions | 3     |
| 01-03-2021 | {"customer":"b"} | Transactions | 575   |
| 01-03-2021 | {"customer":"b"} | Value        | 85    |
| 01-03-2021 | {"customer":"b"} | Transactions | 43    |
| 01-03-2021 | {"customer":"b"} | Value        | 85    |
| 01-03-2021 | {"customer":"c"} | Value        | 789   |

I'm trying to write a query that will find for each customer the max of each value of each type, e.g. something like:

| date       | customer | Type         | value |
| ---------------------------------------------|
| 01-03-2021 | a        | Transactions | 50    |
| 01-03-2021 | a        | Value        | 784   |
| 01-03-2021 | b        | Transactions | 575   |
| 01-03-2021 | b        | Value        | 85    |
| 01-03-2021 | c        | Transactions | 733   |
| 01-03-2021 | c        | Value        | 789   |

I'm struggling to know what concept in kusto to search for to do this sort of operation. I can get a distinct list of customers and a distinct list of types, but I'm not sure how to combine the two, or if that's even what I should be doing!

Any clues would be helpful!

Answer 1

Using summarize arg_max(...) by Type, Customer will do the trick.

See more on arg_max here.