How many join conditions should be there to avoid a Cartesian Join for joining three tables?
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1
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2
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3
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None of those
To avoid a Cartesian product when joining N tables, you need N-1 join conditions. For three tables, this means 2 join conditions are required. With fewer conditions, the database creates a Cartesian product between the unjoined tables.
To avoid a Cartesian Join when joining three tables, you need to have join conditions that link the tables together. A Cartesian Join occurs when there are no join conditions specified, resulting in a combination of all rows from each table.
Let's go through each option to understand why it is correct or incorrect:
Option A) 1 - This option is incorrect. Having only one join condition would still result in a Cartesian Join. You need to specify join conditions that link all three tables together.
Option B) 2 - This option is correct. To avoid a Cartesian Join when joining three tables, you need to have at least two join conditions. This ensures that each table is properly linked to the other two, preventing a Cartesian Join.
Option C) 3 - This option is incorrect. While having three join conditions might work in some cases, it is not necessary to avoid a Cartesian Join when joining three tables. Two join conditions are sufficient.
Option D) None of those - This option is incorrect. The correct answer is B, as explained above.
The correct answer is B. This option is correct because having two join conditions is necessary to avoid a Cartesian Join when joining three tables.