Chapter 6: Problem 27

In a tuple relational calculus query with \(n\) tuple variables, what would be the typical minimum number of join conditions? Why? What is the effect of having a smaller number of join conditions?

Short Answer

Expert verified

The typical minimum number of join conditions in a tuple relational calculus query with \(n\) tuple variables would generally be \(n-1\). This is to ensure that each tuple is connected to at least one other tuple. If we have fewer join conditions, it could result in a larger result set, as there are fewer restrictions on the tuples that can combine, resulting in a broader selection of data.

Step by step solution

Understand Tuple Relational Calculus

The tuple relational calculus (TRC) is a type of non-procedural, declarative database query language. It is non-procedural because it allows the user to state what they want (a result) without specifically stating how to obtain it.

Analyze join conditions in Tuple Relational Calculus

Join conditions in TRC represent the prerequisites under which two tuples, from two relations, can be combined. If there are \(n\) tuple variables, the typical minimum number of join conditions is \(n-1\). This happens because each tuple variable needs to be connected by a join condition with at least one other tuple variable. Hence when we have \(n\) tuple variables, we would typically need \(n-1\) join conditions to connect each tuple with at least other one.

Understand the effect of fewer join conditions

If there are fewer join conditions than the minimum, it would generally result in a larger result set. This is because fewer join conditions mean fewer restrictions on the tuples that can be combined, resulting in a broader data selection.

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In a tuple relational calculus query with \(n\) tuple variables, what would be the typical minimum number of join conditions? Why? What is the effect of having a smaller number of join conditions?

Short Answer

Step by step solution

Understand Tuple Relational Calculus

Analyze join conditions in Tuple Relational Calculus

Understand the effect of fewer join conditions

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