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SELECT S.rating, MIN (S.age) AS minage FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating

SELECT S.rating, MIN (S.age) AS minage FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating HAVING COUNT (*) > 1. Step 1: Evaluate FROM subqueries. Helps to think of it like: FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating SELECT S.rating, MIN (S.age) AS minage HAVING COUNT (*) > 1.

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SELECT S.rating, MIN (S.age) AS minage FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating

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  1. SELECT S.rating, MIN (S.age) AS minage FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating HAVING COUNT (*) > 1

  2. Step 1: Evaluate FROM subqueries Helps to think of it like: FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating SELECT S.rating, MIN (S.age) AS minage HAVING COUNT (*) > 1 Nothing to see here!

  3. Step 2: evaluate WHERE FROM Sailors S WHERE S.age >= 18 GROUP BY S.rating SELECT S.rating, MIN (S.age) AS minage HAVING COUNT (*) > 1

  4. Step 3: GROUP BY S.rating

  5. Step 4: SELECT S.rating, MIN (S.age) AS minage Keeping the original rows around…

  6. Step 5: HAVING COUNT (*) > 1 … for the HAVING clause!

  7. Result Takeaway: since groups are not formed yet, trying to do an aggregate expression in the WHERE clause doesn’t make sense in this model of SQL evaluation.

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