Define the term tuple, attribute and relation. Discuss the difference between a relation and a table....

Define the term tuple, attribute and relation.
Discuss the difference between a relation and a table.
What constitutes union compatibility?
What is a Cartesian Product operation?
When must a GROUP BY clause be used in a query?
Explain functional dependency between two attributes?

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Expert Solution

A tuple is a row in a table or it is a record of a table or it is a ordered set of values. It represents some facts that corresponds to real world entity. An attribute is the columns in a table. All the values under an attribute is derived from an appropriate domain. Set of tuples or rows are known as a relation .
The main difference between a table and a relation is that, a table is a collection of values which can contain duplicate values. Relation can also be called as a table, but it is a set of values that are un-ordered and there should not be any duplicate values.
For two relations to be union compatible, they should have same number of attributes and similar attributes should belong to same domain (i.e., domain of jth attribute of a relation and domain of jth attribute of another relation should be same).
Cartesian Product combines the tuples of a relation with the tuples of another relation. It also known as cross product.
A GROUP BY clause is mainly used with a SELECT statement to group rows that have identical values( it will group all the identical rows and a return a single row).
A set of attributes X functionally determines a set of attributes Y if the value of X determines a unique value for Y( i.e., one attribute uniquely determines another attribute). It is a constraint between two attributes.

venereology answered 10 months ago

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