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Exercise #7 page 3

It is possible to use a table join instead of the IN predicate; however, SQL Server builds identical execution plans for both cases.

  1. SELECT a.model, price
  2. FROM (SELECT model, price
  3. FROM PC
  4. UNION
  5. SELECT model, price
  6. FROM Laptop
  7. UNION
  8. SELECT model, price
  9. FROM Printer
  10. ) AS a JOIN
  11. Product p ON a.model = p.model
  12. WHERE p.maker = 'B';

Queries based on table joins can be an alternative to union queries. For this particular task, such a solution has a less efficient execution plan, but in other cases it may prove to be preferable. Anyway, for learning purposes, it makes sense to try different ways of solving the task, which is left as an exercise to the reader.


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