Exercise #46 page 3

In conclusion, I adduce one more solution with such mistake, but without using outer joins.

Solution 3.1.3

Console

Execute

SELECT a.ship, b.displacement, b.numguns
FROM Outcomes a, Ships c, Classes b
WHERE a.battle='Guadalcanal' AND
 a.ship = c.name AND
 c.class = b.class
UNION
SELECT a.ship, NULL AS displacement, NULL AS numguns
FROM Outcomes a
WHERE a.battle = 'Guadalcanal' AND
 a.ship NOT IN (SELECT name 
 FROM Ships
 );

Let`s note that the first offered solution would return right result for such lead ship. That`s why that to solve this task we need to append the first solution to the second. The ways how should not to "append" solution, you can see in the Chapter four.

T&S

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mistakes outer joins ships Guadalcanal exercise 46

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S. I. Moiseenko

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Database «Ships»

Exercise #46 page 3