Exercise #54 (tips and solutions) |
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In order to employ UNION in the solution 3.10.2, it is not enough to perform unioning by only numGuns column. It is required of a list of columns that it should determine a ship unambiguously. Then duplicates rather then useful information will actually be excluded. Below, a solution is presented which makes use of this expedient but contains a small mistake. And we leave it to the reader to find it.
To return to discussion of exercise #54 To solve a problem on SQL-EX.RU |