Setting date to local variable from data query - "No tabular expression statement found"

Question

I am unable to set a scalar date value from a query to a local variable. I get the following error:

SYNTAX ERROR

No tabular expression statement found

Query:

let startTime = toscalar(customMetrics
| where timestamp > ago(1d)
| summarize min(timestamp));

I get a result just fine when running just the query:

What am I doing wrong?

Answer 1

You'd need to execute a statement/query with this function, otherwise it's just a function definition that does not get called. The easiest one is print command, but you can also invoke the function within some query:

let startTime = toscalar(customMetrics
| where timestamp > ago(10m)
| summarize min(timestamp));
print startTime