Question
Which of the following integrity constraints ensures
that every non-null foreign key value must reference an existing primary key value in another table?Solution
Referential integrity enforces a relationship between two tables by ensuring that a foreign key in one table matches a valid primary key in another table. This constraint guarantees that the data is consistent and prevents "orphan" records. For example, in an "Orders" table with a foreign key referencing a "Customers" table, referential integrity ensures that every order must belong to an existing customer. If a foreign key value does not match any primary key value in the referenced table, the database system will reject the operation, ensuring data consistency. Why Other Options Are Incorrect:
- Option A: Entity integrity relates to primary keys, ensuring they are unique and not NULL. It does not address relationships between tables.
- Option C: Domain integrity enforces the validity of data types and permissible values for attributes, such as ensuring an "age" column only contains integers.
- Option D: Key integrity is not a formal term in relational database theory. It may be confused with primary or candidate key constraints but is not relevant here.
- Option E: Tuple integrity is not a standard concept in relational databases, making this option invalid.
Statements: M % N, N & A, A @ B, B # C
Conclusions: I. C & AÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â II. M # B
...Statements: P # B, Q $ B, B @ J, J % F
Conclusions: Â Â Â Â Â I. F # BÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â II. F @ BÂ Â Â Â Â Â Â Â Â Â Â Â Â Â ...
Statement: C < D ≤ E; F > E ≤ G ; D ≥ H
Conclusions: I. G = H II. G > H
...In the question, assuming the given statements to be true, find which of the conclusion (s) among given three conclusions is /are definitely true and ...
In the question, assuming the given statements to be true, find which of the conclusion (s) among given two conclusions is /are definitely true and the...
Statements: A < B; C = D; B >E ≥ C
Conclusions:
I. A < C
II. E = D
Which of the following symbols respectively should replace the question marks in order to make the expression V ≥ M and X ≤ H definitely true?
<...In the question assuming the given statements to be true, find which of the conclusion(s) among given three conclusions is/are definitely true and then...
In the question, assuming the given statements to be true, find which of the conclusion (s) among given three conclusions is/are definitely true and th...
Statements:
M < K ≤ G ≤ Z; P = J > Z; I ≥ R > P;
Conclusions:
I. K ≤ P
II. M < R
