GROUP BY clause

Let's now receive the number of the computers those RAM-suitable to each type of operational system. Then we can write the following query:

  2. CASE
  3. WHEN ram < 64
  4. THEN 'W95'
  5. WHEN ram < 128
  6. THEN 'W98'
  7. ELSE 'W2k'
  8. END Type,
  9. COUNT(*) Qty
  10. FROM PC
  11. GROUP BY
  12. CASE
  13. WHEN ram < 64
  14. THEN 'W95'
  15. WHEN ram < 128
  16. THEN 'W98'
  17. ELSE 'W2k'
  18. END

As a result of running query we shall receive:

Type Qty
W2k 5
W95 3
W98 3

Here we duplicate CASE operator in SELECT clause to receive a column with the name of operational system.

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