All Categories MCQs
Topic Notes: All Categories
General Description
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
341
A candidate key is an attribute or a set of attributes that:
Answer:
Could potentially be chosen as the table's primary key.
A candidate key is any column or combination of columns that can qualify as a unique identifier for the rows in a table. A table can have multiple candidate keys, from which one is selected to be the primary key.
342
A key that links a weak entity to its owner (strong) entity is a type of:
Answer:
Foreign Key
The relationship between a weak entity and its strong entity is maintained by a foreign key in the weak entity table that references the primary key of the strong entity table.
343
What is a "fully functional dependency"?
Answer:
When an attribute is dependent on the entire composite primary key, not just a part of it.
A fully functional dependency exists if an attribute Y is functionally dependent on a composite key X, but not on any proper subset of X. The concept is central to the definition of 2NF.
344
In a foreign key constraint, the `ON DELETE CASCADE` action specifies that:
Answer:
When a parent record is deleted, all corresponding child records should also be deleted.
`ON DELETE CASCADE` is a referential action that automatically deletes all matching records in the child table when a record in the parent table is deleted. This helps maintain referential integrity automatically.
345
The 'Entity Integrity' constraint states that:
Answer:
A primary key value cannot be NULL.
The entity integrity rule is a fundamental constraint of the relational model. It specifies that no attribute participating in the primary key of a table is allowed to have a NULL value.
346
A 'domain' in the relational model refers to:
Answer:
A set of permissible values for an attribute.
The domain of an attribute is the set of all unique, atomic values that the attribute can validly contain. For example, the domain for a 'Gender' attribute might be {'Male', 'Female', 'Other'}.
347
Which of the following contains information about the structure of a database?
Answer:
Data dictionary
A data dictionary, or metadata repository, contains information about the database's structure, including tables, columns, data types, and constraints.
348
What term is used for a collection of information to build reports or analyze data in an environment?
Answer:
Database
A database is a structured collection of data that can be analyzed and used for reporting.
349
The 'data dictionary' or 'system catalog' stores what type of information?
Answer:
Metadata
The data dictionary is a component of the DBMS that stores metadata. This includes information about schemas, tables, columns, data types, constraints, user permissions, and other structural information about the database.
350
What is a superkey?
Answer:
A set of attributes that can uniquely identify a tuple.
A superkey is a set of one or more attributes that, when taken together, can uniquely identify a record in a table. A candidate key is a minimal superkey, meaning it's a superkey from which no attributes can be removed without losing the uniqueness property.