Semantic error: Unresolved reference binding: 'idx'

Question

Hi Team, When I am running the below query, it failed with the error "Semantic error: Unresolved reference binding: 'idx'", Please can anyone help with this?

let wau = (cDate:datetime) { 
toscalar(customEvents
| where timestamp > cDate - 7d and timestamp < cDate
| summarize dcount(user_Id))
};
range idx from datetime(2022-12-01) to now() step 1d 
| extend wau(idx)

If I use now() as a parameter, the query is running fine.

| extend wau(now())

Answer 1

Hi Anvesh Kasani,

Thank you for posting query in Microsoft Q&A Platform.

You are hitting this failure because of limitations of toscalar()function. toscalar()function cannot be applied on a scenario where function applies on each row. click here to know more about it.

For example, below code results in same error which you are facing.

let _dataset2 = datatable(x:long, y:long) [ 1, 2, 3, 4, 5, 6];
let tg = (x_: long)
{
    toscalar(_dataset2| where x == x_ | project y);
};
_dataset1
| extend y = tg(x)

To avoid error where we can use join operator as below.

let _dataset1 = datatable(x: long)[1, 2, 3, 4, 5];
let _dataset2 = datatable(x: long, y: long) [1, 2, 3, 4, 5, 6];
_dataset1
| join (_dataset2) on x 
| project x, y

Hope this helps.

---

Please consider hitting Accept Answer button. Accepted answers help community as well.