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Custom classifications of business objects
Custom grouping of business objects
Custom counting of business objects
14. Summing of business values


Perfect! Suppose we now want to show the total amount paid for each order alongside the amount paid for non-vegetarian products. Take a look:

  SUM(Quantity * OI.UnitPrice) AS TotalPrice,
    WHEN P.CategoryID in (6, 8) THEN Quantity * OI.UnitPrice
    ELSE 0
  END) AS NonVegetarianPrice
FROM Orders O
JOIN OrderItems OI
  ON O.OrderID = OI.OrderID
JOIN Products P
  ON P.ProductID = OI.ProductID

So far, we wrote the queries with SUM(CASE WHEN...) in such a way that they could all be replaced with equivalent COUNT(CASE WHEN...) constructions. Here, however, SUM(CASE WHEN...) is the only option – we want to sum certain values (OI.Quantity * OI.UnitPrice) instead of merely counting rows.


This time, we want a report that will show each supplier alongside their number of units in stock and their number of expensive units in stock. Show four columns: SupplierID, CompanyName, AllUnits (all units in stock supplied by that supplier), and ExpensiveUnits (units in stock with a unit price over 40.0, supplied by that supplier).

Stuck? Here's a hint!

JOIN the Products and Suppliers tables. Group by SupplierID and CompanyName.