Add support for unit conversion
Please add a "Canonical UOM Per UOM" or "UOM Per Canonical UOM" column (not necessarily with those exact names) to the UnitOfMeasure table. This column would contain the conversion factor needed to convert between the UOM and the canonical UOM, similar to the "Canonical" column in PI System Explorer when you are viewing a UOM class.
With this in place, a user can easily convert a value to any unit by first converting from the value's default UOM to the canonical UOM of the value's UOM class, and then convert from the canonical UOM to the desired UOM. This would take 2 joins or lookups against the UnitOfMeasure table.
Alternatively, or perhaps in addition to the above, add support for a CONVERT function that works like so:
CONVERT(number, fromUOM, toUOM)
This would be more similar to the CONVERT function in Excel than the Convert function in PI Asset Analytics.