Matthew Hicks shows how to use Powershell to parameterize U-SQL scripts:
You can use this feature either via Azure Cloud Shell or on a Windows machine with Azure PowerShell installed.
When submitting, simply construct a hashtable of U-SQL variable names to values and pass it in using the -ScriptParameter cmdlet parameter. The .NET type of each value in the hashtable is used when defining the variable in U-SQL.
Supported types include:
byte, sbyte, int, uint (or uint32), long, ulong (or uint64), float, double, decimal, short (or int16), ushort (or uint16), char, string, DateTime, bool, Guid, or byte[]
Read on for an example of the process.