Use Variables in Kusto
In kusto, there are basically two types of data, one is tabular, another is scalar. By using let operator, you can predefine some parameters before a tabular querying. now, how should you do if you want to reassign the parameters in a the middle of a query? just like Variable do in a general programming language.
Yes, we can easily achieve it by using toscalar() function. for example:
let max_date_tabular = sample_table | summarize max_date = max(Timestamp); let max_date = toscalar(max_date_tabular); data_table | where date_time > datetime_add('month',-1,max_date) | take 10
in this script, first, I get the max date value from sample_table, but now, the date is still in tabular format, we can't use it in a where statement. Next, I use toscalar() function to convert the tabular data to scalar value. and I can now use it in my next query.