Trouble Spots

Question 1

SELECT (RESTRICT) yields a horizontal subset of a single table.

Answer 1

True

Question 2

PROJECT yields a vertical subset of a single table.

Answer 2

True

Question 3

UNION combines all rows from two tables excluding duplicate rows. The columns and domains of the two tables must be compatible.

Answer 3

True

Question 4

INTERSECT yields only the rows that appear in both tables. Tables must be union-compatible.

Answer 4

True

Question 5

DIFFERENCE yields all rows in one table that are not found in the other; that is it subtracts one table from another. Tables must be union-compatible.

Answer 5

True

Question 6

PRODUCT yields all possible pairs of rows from two tables.

Answer 6

True

Question 7

NATURAL JOIN links tables by selecting only the rows with common values in their common attributes.

Answer 7

True

Question 8

INNER JOIN only returns matched records from the tables being joined.

Answer 8

True

Question 9

OUTER JOIN returns the matched pairs of the inner join plus the unmatched records from one of the tables.

Answer 9

True

Question 10

LEFT OUTER JOIN yields all the rows in the left table including those that have no matching values in the other table

Answer 10

True

Question 11

RIGHT OUTER JOIN yields all the rows in the right table including those that have no matching values in the other table

Answer 11

True

Question 12

DIVIDE is used to answer questions about one set of data being associated with all values in another set. DIVIDE uses one double-column table as the dividend and one single-column table as the divisor.

Answer 12

True

Question 13

All information in a relational database must be logically represented as column values in rows within tables.

Answer 13

Information; Rule 1

Question 14

Every value in a table is guaranteed to be accessible through a combination of table name, primary key value, and column name.

Answer 14

Guaranteed access; Rule 2

Question 15

Nulls must be represented and treated in a systematic way, independent of data type.

Answer 15

Systematic treatment of nulls; Rule 3

Question 16

The metadata must be stored and managed as ordinary data - that is, in tables within the database; such data must be available to authorized users using the standard database relational language.

Answer 16

Dynamic online catalog based on the relational model; Rule 4

Question 17

The relational database may support many languages; however it must support one well-defined, declarative language as well as data definition, view definition, data manipulation (interactive and by program), integrity constraints, authorization, and transaction management (begin, commit, and rollback).

Answer 17

Comprehensive data sublanguage; Rule 5

Question 18

Any view that is theoretically updatable must be updatable through the system.

Answer 18

View updating; Rule 6

Question 19

The database must support set-level inserts, updates, and deletes.

Answer 19

High-level insert, update, and delete; Rule 7

Question 20

Application programs and ad-hoc facilities are logically unaffected when physical access methods or storage structures are changed.

Answer 20

Physical data independence; Rule 8

Question 21

Application programs and ad-hoc facilities are logically unaffected when changes are made to the table structures that preserve the original table values (changing order of columns or inserting columns).

Answer 21

Logical data independence; Rule 9

Question 22

All relational integrity constraints must be definable to the relational language and stored in the system catalog (not at the application level).

Answer 22

Integrity independence; Rule 10

Question 23

If the system supports low-level access to the data, users must not be allowed to bypass the integrity rules of the database.

Answer 23

Non-subversion; Rule 12

Question 24

The end users and application programs are unaware of and unaffected by the data location (distributed vs. local databases).

Answer 24

Distribution independence; Rule 11

Question 25

All proceeding rules are based on the notion that to be considered relational, a database must use its relational facilities exclusively for management.

Answer 25

Rule 0