Miscelaneous Database Stuff For The Final

Front 1

T/F The relational always produces a relation with no duplicate tuples?

Back 1

True

Front 2

T/F In an SQL query, the SELECT clause is evaluated after all its other clauses.

Back 2

True

Front 3

SELECT Essn
FROM WORKS_ON
WHERE Pno IN (1,2,3);
The (1,2,3) in this WHERE statement are an example of what?

Back 3

explicit set of values.

Front 4

What do instance variables do?

Back 4

hold values that define internal state of object

Front 5

What are the two parts of Operations?

Back 5

Signature/interface and Implementation

Front 6

What does the cardinality function do?

Back 6

Returns the current number of elements in an array

Front 7

What does a Reference type object do?

Back 7

Creates unique system-generated object identifiers

Front 8

T/F The relational calculus is a more procedural formalism, compared to the relation algebra which is more declarative.

Back 8

False

Front 9

T/F The FROM clause of a SELECT statement performs a natural join of all the tables in its list.

Back 9

False

Front 10

T/F The relational algebra and relation calculus are equivalent in expressive power.

Back 10

True

Front 11

T/F In the E/R model, a property might be missing if is not applicable for an entity instance?

Back 11

False

Front 12

T/F Whether a relationship is 1:N or N:1 is merely a matter of perspective; we make no formal distinction between the two possibilities.

Back 12

False

Front 13

T/F A weak entity is one that is no longer essential within the database; it is obsolete.

Back 13

False

Front 14

T/F Composite attributes can be composed of other composite attributes. In other words, the compositionality of attributes can forma hierarchy

Back 14

True

Front 15

T/F An identifying relationship relates a weak entity to its own.

Back 15

True

Front 16

T/F The number of tuples in A x B is the number of tuples in A plus the number of tuples in B

Back 16

False

Front 17

T/F The order of columns in a table is not significant in a relational schema

Back 17

False

Front 18

T/F Entities and relationships are both mapped to relations in the transition from conceptual to logical models

Back 18

True

Front 19

T/F A participation constraint specifies whether the existence of an entity is dependent on the existence of another entity via a relationship.

Back 19

False

Front 20

T/F A superkey is a set of attributes, each of which is unique independently from the rest.

Back 20

True

Front 21

When mapping a 1:N relationship to the relational model, the standard approach is ?

Back 21

the primary key of the one side appears as a foreign key on the many side.

Front 22

In a baseball database that tracks statistics over many years, the relationship between player and team is ?

Back 22

N:M

Front 23

In a congressional database, the relationship between congressman and district is what kind of participation?

Back 23

Total for both?

Front 24

When the primary key from a relation appears as an attribute (or attributes) in another relation, it is referred to as a ?

Back 24

foreign key

Front 25

When mapping from an E/R to a Relational model composite attributes in the E/R model are ?

Back 25

flattened to just the simple component attributes in the relational model

Front 26

When mapping from an E/R to a Relational model if there are multiple keys for an entity in the E/R model than?

Back 26

then there will be the one of them will be selected to be the primary key in the relational model.

Front 27

The three-schema architecture of database systems refers to?

Back 27

internal (physical) level, conceptual level, and external (view) level

Front 28

The degree of a relations refers to what?

Back 28

the number of attributes it has

Front 29

Referential and key constraints are examples of what in the relational model?

Back 29

Explicit constraints

Front 30

You can add a row using SQL in a database with command?

Back 30

INSERT

Front 31

T/F A right outer join includes all the tuples from both relations satisfying the join condition, along with all the tuples in the right relation that do not have a corresponding tuple in the left relation.

Back 31

True

Front 32

Two relations are union compatible if they have the same number of ?

Back 32

attributes

Front 33

The relational algebra operations enable a user to specify basic?

Back 33

data retrieval