PREVIOUS YEAR SOLVED PAPERS - JULY 2016 Paper 2
16. In RDBMS, the constraint that no key attribute (column) may be NULL is referred to as:
- Option : C
- Explanation :
- In RDBMS, the constraint that no key attribute (column) may be NULL is referred to as Entity Interity
- Referential integrity states that table relationships must always be consistent.
- Multi-valued dependencyis a full constraint between two sets of attributes in a relation
- Functional dependency is a relationship that exists when one attribute uniquely determines another attribute.
So, option (C) is correct.
- Option : D
- Explanation :
- Views in a database system are important because they help with access control by allowing users to see only a particular subset of the data in the database.Correct
- E-R diagrams are useful to logically model concepts.Inorrect
- An update anomaly is when it is not possible to store information unless some other, unrelated information is stored as well.Inorrect
- SQL is a procedural language.Inorrect
So, option (D) is correct.
18. In a relational database model, NULL values can be used for all but which one of the following ?
- A
To allow duplicate tuples in the table by filling the primary key column(s) with NULL.
- B
To avoid confusion with actual legitimate data values like 0 (zero) for integer columns and ’’ (the empty string) for string columns.
- C
To leave columns in a tuple marked as ’’unknown’’ when the actual value is unknown.
- D
To fill a column in a tuple when that column does not really ”exist” for that particular tuple.
| A | B | C | D |
| a1 | b1 | c1 | d1 |
| a2 | b3 | c3 | d1 |
| a1 | b1 | c1 | d2 |
