DBMS MCQ — 3 Practice Questions with Answers

Explanation

A foreign key value in the child relation must match an existing primary-key value in the parent relation. Inserting a tuple into R2 can violate this if its foreign key has no matching R1 row, and deleting a tuple from R1 can violate it if R2 still refers to that parent row. Therefore, both operations may violate referential integrity, so option C is correct.

Explanation

In the ER model, an entity is described by a set of attributes. Attributes store the properties of that entity, such as name, roll number, or address for a student entity. Relationships connect entities, so option B does not represent an entity by itself.

Explanation

Microsoft's DataTable event list includes RowChanged, ColumnChanged, and RowChanging. Since all three listed events are exposed by the DataTable object, the combined choice is correct. Therefore, option D is correct.