MCQ IN COMPUTER SCIENCE & ENGINEERING

COMPUTER SCIENCE AND ENGINEERING

SQL

 Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
The ____ specification says that the values of attributes (Ak1, Ak2, . . ., Akn ) for any tuple in the relation must correspond to values of the primary key attributes of some tuple in relation s.
 A Super Key B Primary Key C Foreign Key D None of the above
Explanation:

Detailed explanation-1: -Functional Dependencies A functional dependency (FD) is a constraint between two sets of attributes. This constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X], then they have t1[Y] = t2[Y]. This means the value of the X component of a tuple uniquely determines the value of component Y.

Detailed explanation-2: -In the relationship window in Access, the primary key side of a one-to-many relationship is denoted by a number 1. The foreign key side of a relationship is denoted by an infinity symbol.

Detailed explanation-3: -Select () Select operation is done by Selection Operator which is represented by “sigma"(). It is used to retrieve tuples(rows) from the table where the given condition is satisfied. It is a unary operator means it requires only one operand.

Detailed explanation-4: -Union Operation: Suppose there are two tuples R and S. The union operation contains all the tuples that are either in R or S or both in R & S. It eliminates the duplicate tuples. It is denoted by ∪.

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