u sql - Convert Rowset variables to scalar value

Question

Is it possible to convert rowset variables to scalar value for eg.

@maxKnownId =
    SELECT MAX(Id) AS maxID
    FROM @PrevDayLog;

DECLARE @max int = @maxKnownId;

Answer 1

There is no implicit conversion of a single-cell rowset to a scalar value in U-SQL (yet).

What are you interested in using the value for?

Most of the time you can write your U-SQL expression in a way that you do not need the scalar variable. E.g., if you want to use the value in a condition in another query, you could just use the single value rowset in a join with the other query (and with the right statistics, I am pretty sure that the optimizer would turn it into a broadcast join).

If you feel you cannot easily write the expression without the rowset to a scalar, please let us know via http://aka.ms/adlfeedback by providing your scenario.