Vertabelo is great but it's missing Computed Columns feature, at least in SQL Server projects.
So Calculated Columns are created like this (Inventory), and I really think that implementing this feature for you is not a big trouble.
CREATE TABLE dbo.Products ( ProductID int IDENTITY (1,1) NOT NULL , QtyAvailable smallint , UnitPrice money , InventoryValue AS QtyAvailable * UnitPrice );
Full documentation on https://msdn.microsoft.com/en-us/library/ms188300.aspx
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