Clauses such as
HAVING (among others) allow you to enter U-SQL expressions.
An expression in a programming language is a combination of explicit values, constants, variables, operators, and functions that are interpreted according to the particular rules of precedence and of association for a particular programming language, which computes and then produces another value.
The simplest way of thinking of a U-SQL expression is that it is a merely C# expression with some U-SQL extensions such as the
Expressions can also be converted to a different type
@output= SELECT Start, Region, ((double) Duration) AS DurationDouble FROM @searchlog;
Calling methods .NET Types
RowSet columns are strongly typed. U-SQL allows you to call methods defined on those types in the SELECT clause. Because U-SQL supports .NET types such as string and DateTime, you can use all the methods available on those types.
// Find what day of year each session took place @output= SELECT Start, Region, Start.DayOfYear AS StartDayOfYear FROM @searchlog;