Q&A Hero

Q: The CHECK constraint is used to define a condition for the values that the attribute domain cannot have.

Q: Entity integrity is enforced automatically when the primary key is specified in the CREATE TABLE command sequence.

Q: Only numeric data types can be added and subtracted in SQL.

Q: Data type selection is usually dictated by the nature of the data and by the intended use.

Q: SQL is considered difficult to learn; its command set has a vocabulary of more than 300 words.

Q: The ANSI SQL standards are also accepted by the ISO.

Q: The ANSI prescribes a standard SQL"the current fully approved version is known as SQL-07.

Q: A database language enables the user to perform complex queries designed to transform the raw data into useful information.

Q: A database language enables the user to create database and table structures to perform basic data management chores.

Q: Tables within a database share common attributes that enable the tables to be linked together.

Q: Depending on the sophistication of the application development software, nulls can create problems when functions such as COUNT, AVERAGE, and SUM are used.

Q: There is never a good reason to use null values in a database.

Q: A null is created when you press the Enter key or the Tab key to move to the next entry without making a prior entry of any kind.

Q: If the attribute (B) is functionally dependent on a composite key (A) but not on any subset of that composite key, the attribute (B) is fully functionally dependent on (A).

Q: Only a single attribute, not multiple attributes, can define functional dependence.

Q: In a relational model, if A determines B, C, and D, you write A = B, C, D.

Q: The idea of determination is unique to the database environment.

Q: Each table in a relational database must have a primary key.

Q: Character data can contain any character or symbol intended for mathematical manipulation.

Q: Numeric data are data on which you can perform meaningful arithmetic procedures.

Q: The order of the rows and columns is important to the DBMS.

Q: Because the relational model uses attribute values to establish relationships among tables, many database users correctly assume that the term relation refers to such relationships.

Q: You can think of a table as a persistent representation of a logical relation.

Q: The practical significance of taking the logical view of a database is that it serves as a reminder of the simple file concept of data storage.

Q: What is the system catalog?

Q: Describe the use of the UNION operator.

Q: Describe the use of nulls in a database.

Q: What is a key and why is it important in the relational model?

Q: What are the characteristics of a relational table?

Q: Codd's rule of ____________________ states that every value in a table is guaranteed to be accessible through a combination of table name, primary key value, and column name.

Q: The index key can have multiple attributes, this is called a(n) ____________________ index.

Q: A(n) ____________________ index is an index in which the index key can have only one pointer value (row) associated with it.

Q: A(n) ____________________is an orderly arrangement used to logically access rows in a table.

Q: Proper data ____________________ design requires carefully defined and controlled data redundancies to function properly.

Q: The proper use of ____________________ keys is crucial to controlling data redundancy.

Q: Fortunately, the problems inherent in the ____________________ relationship can easily be avoided by creating a composite entity.

Q: ____________________ relationships can be implemented by creating a new entity in 1:M relationships with the original entities.

Q: If one department chaira professorcan chair only one department and one department can have only one department chair, then the entities PROFESSOR and DEPARTMENT exhibit a(n) ____________________ relationship.

Q: ____________________ relationships cannot be implemented as such in the relational model.

Q: The ____________________ relationship is the relational database norm.

Q: The ____________________ catalog can be described as a detailed system data dictionary that describes all objects within the database, including data about table names, the table's creator and creation date, the number of columns in each table, the data type corresponding to each column, index filenames, index creators, authorized users, and access privileges.

Q: A(n) ____________________provides a detailed description of all tables found within the user/designer-created database.

Q: ____________________ joins are especially useful when you are trying to determine what value(s) in related tables cause(s) referential integrity problems.

Q: A(n) ____________________ links tables on the basis of an equality condition that compares specified columns of each table.

Q: ____________________ is the real power behind the relational database, allowing the use of independent tables linked by common attributes.

Q: PRODUCT yields all possible pairs of rows from two tablesalso known as the ____________________ product.

Q: The relational operators have the property of ____________________; that is, the use of relational algebra operators on existing relations (tables) produces new relations.

Q: To avoid nulls, some designers use special codes, known as ____________________, to indicate the absence of some value.

Q: The following example exhibits ____________________ integrity: The CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. Similarly, the AGENT table's primary key is AGENT_CODE, and this primary key column also is free of null entries.

Q: If the foreign key contains either matching values or nulls, the table that makes use of that foreign key is said to exhibit ____________________ integrity

Q: A(n) ____________________ keycan be described as a superkey without unnecessary attributes.

Q: In the relational model, ____________________ are important because they are used to ensure that each row in a table is uniquely identifiable.

Q: In a relational table, each column has a specific range of values known as the ____________________ domain.

Q: The logical view of the relational database is facilitated by the creation of data relationships based on a logical construct known as a(n) ____________________.

Q: Codd's Rule of ____ states:If the system supports low-level access to the data, users must not be allowed to bypass the integrity rules of the databasea. Nonsubversion b. Logical Data Independence c. Comprehensive Data Sublanguaged. Integrity Independence

Q: Codd's Rule of ____ states: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).a. Nonsubversion b. Logical Data Independence c. Comprehensive Data Sublanguaged. Integrity Independence

Q: When you define a table's primary key, the DBMS automatically creates a(n) ____ index on the primary key column(s) you declared.a. key b. incomplete c. uniqued. primary

Q: A(n) ____ is an ordered arrangement of keys and pointers.a. table b. superkey c. relationshipd. index

Q: Another name for a composite entity is a ____ entity.a. bridge b. linked c. directived. referring

Q: Since it is used to link the tables that originally were related in a M:N relationship, the composite entity structure includesas foreign keysat least the ____ keys of the tables that are to be linked.a. composite b. super c. primaryd. unique

Q: The ____ relationship should be rare in any relational database design.a. 1:1 b. 1:M c. M:1d. M:N

Q: The ____ relational type is the "relational model ideal."a. 1:1 b. 1:M c. M:1d. M:N

Q: In a database context, a(n) ____indicates the use of different names to describe the same attribute.a. entity b. duplicate c. synonymd. homonym

Q: In a database context, the word ____indicates the use of the same attribute name to label different attributes.a. redundancy b. homonym c. duplicated. synonym

Q: The ____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents.a. meta dictionary b. schema c. data dictionaryd. system catalog

Q: A ____ contains at least all of the attribute names and characteristics for each table in the system.a. data dictionary b. relational schema c. logical schemad. join

Q: A(n) ____ join only returns matched records from the tables that are being joined.a. outer b. inner c. directd. union

Q: In an outer join, the matched pairs would be retained and any unmatched values in the other table would be left ____. a. in another table b. null c. out of the results d. with matching values from the original table

Q: The equijoin takes its name from the comparison operator ____ used in the condition.a. *b. < c. =d. >

Q: A(n) ____ join links tables by selecting only the rows with common values in their common attribute(s).a. equal b. unique c. foreignd. natural

Q: ____ yields only the rows that appear in both tables.a. INTERSECT b. UNION c. DIFFERENCEd. SELECT

Q: ____ combines all rows from two tables, excluding duplicate rows.a. INTERSECTb. UNION c. DIFFERENCEd. SELECT

Q: ____ yields a vertical subset of a table.a. PROJECTb. SELECT c. UNIONd. DIFFERENCE

Q: ____, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.a. INTERSECT b. UNION c. DIFFERENCEd. SELECT

Q: To be considered minimally relational, the DBMS must support the key relational operators ____, PROJECT, and JOIN.a. INTERSECT b. UNION c. DIFFERENCEd. SELECT

Q: The ____ constraint can be placed on a column to ensure that every row in the table has a value for that column.a. HAS VALUE b. NOT NULL c. MUST HAVE VALUEd. NOT EMPTY

Q: A CUSTOMER table's primary key is CUS_CODE. The CUSTOMER primary key column has no null entries, and all entries are unique. This is an example of ____ integrity.a. entity b. referential c. completed. null

Q: All primary key entries are unique, and no part of a primary key may be ____.a. zero b. a foreign key c. nulld. a candidate key

Q: A ____ key can be described as a superkey without unnecessary attributes, that is, a minimal superkey.a. secondary b. candidate c. primaryd. foreign

Q: A ____ key is defined as a key that is used strictly for data retrieval purposes.a. lookup b. foreign c. candidated. secondary