Data Management - Applications
Define this symbol: ⨝
JOIN
This operation retrieves one or more rows of a table, depending on whether the search argument is a unique or non-unique attribute.
Relational Select
Which of the following queries will output the table contents when the value of the character field P_CODE is alphabetically less than 1558-QW1?
SELECT P_CODE, P_DESCRIPT, P_QOH, P_MIN, P_PRICE FROM PRODUCT WHERE P_CODE <'1558-QW1';
_________________ exists when the primary key of the related entity contains a primary key component of the parent entity.
Strong Relationship
A combination of columns that individually identifies any tuple within a database table
Superkey
A ________________entity is generally used to transform M:N relationships into 1:M relationships.
composite
The label "__________________" is based on the fact that the composite entity contains at least the primary key attributes of each of the entities that are connected by it. The composite entity is an important component of the ER model because relational database models should not contain M:N relationships - and the composite entity can be used to break up such relationships into 1:M relationships.
composite
With the exception of the database _____________ process, most RDBMS vendors use SQL that deviates little from the ANSI standard SQL.
creation
The _____________ condition is generally composed of an equality comparison between the foreign key and the primary key of related tables.
join
Explanation: To be classified as a ________ entity, two conditions must be met: -The entity must be existence-dependent on its parent entity. -The entity must inherit at least part of its primary key from its parent entity.
weak
A(n) _______________ character is a symbol that can be used as a general substitute for other characters or commands.
wildcard (or wild card)
A database user manual notes that, "The file contains two hundred records, each record containing nine fields." Use appropriate relational database terminology to "translate" that statement.
"the table -- or entity set -- contains two hundred rows -- or, if you like, two hundred tuples, or entities. Each of these rows contains nine attributes."
A column or set of columns in a table that can uniquely identifies any database row without referring to any other data
Candidate key
The _____ command would be used to delete the table row where the P_CODE is 'BRT-345'.
DELETE FROM PRODUCT WHERE P_CODE = 'BRT-345';
Why are entity integrity and referential integrity important in a database?
Entity integrity and referential integrity are important because they are the basis for expressing and implementing relationships in the entity relationship model.
What does it mean to say that a database displays both entity integrity and referential integrity?
Entity integrity describes a condition in which all tuples within a table are uniquely identified by their primary key. The unique value requirement prohibits a null primary key value, because nulls are not unique. Referential integrity describes a condition in which a foreign key value has a match in the corresponding table or in which the foreign key value is null. The null foreign key "value" makes it possible not to have a corresponding value, but the matching requirement on values that are not null makes it impossible to have an invalid value.
A weak relationship exists if the primary key of the related entity contains at least one primary key component of the parent entity. (T/F)
False
Character data can contain any character or symbol intended for mathematical manipulation. (T/F)
False
Type of JOIN: Returns all rows from the left table and from the right table. It combines the output of both left and right joins.
Full
_____________appear when more than one attribute has the same name
Homonyms
This type of JOIN returns all rows from various tables where the join condition is satisfied. It is the most commonly used type of join.
Inner
In which of the following operations can referential integrity problems occur?
Insert, Delete, Update
_____ relationships cannot be implemented as such in the relational model.
M:N
Type of JOIN: Yields a new table composed of only the rows with common values in their common attributes. It is a three-stage process.
Natural
This operation integrates data from two or more tables or combines them. A join operation can be implemented in the FROM and WHERE clauses.
Project
This operation retrieves all rows and some attributes of a table without using a WHERE clause to limit which rows of the table are included.
Relational Project
Type of JOIN: Returns all rows from the right table, and the matched rows from the left table. The result is NULL in the left side when there is no match.
Right outer
To list all the contents of the PRODUCT table, a user would use _____.
SELECT * FROM PRODUCT
The query used to list the P_CODE, P_DESCRIPT, P_INDATE, and P_PRICE fields from the PRODUCT table in ascending order by P_PRICE is _____.
SELECT P_CODE, P_DESCRIPT, P_INDATE, P_PRICE FROM PRODUCT ORDER BY P_PRICE; (Key word in this one is ORDER)
Single-valued attributes vs. Simple attributes
Single-Valued aren't necessarily simple: For example, an inventory code HWPRIJ23145 may refer to a classification scheme in which HW indicates Hardware, PR indicates Printer, IJ indicates Inkjet, and 23145 indicates an inventory control number. Therefore, HWPRIJ23145 may be decomposed into its component parts... even though it is single-valued Simple attributes: A simple attribute is one that cannot be decomposed into its component pieces. For example, a person's sex is classified as either M or F and there is no reasonable way to decompose M or F. Similarly, a person's first name cannot be decomposed into meaningful components.
_____________ exist when the same attribute has more than one name.
Synonyms
Which relational algebra operators can be applied to a pair of tables that are not union-compatible?
The Product, Join, and Divide operators can be applied to a pair of tables that are not union-compatible. Divide does place specific requirements on the tables to be operated on; however, those requirements do not include union-compatibility. Select (or Restrict) and Project are performed on individual tables, not pairs of tables. (Note that if two tables are joined, then the result is a single table and the Select or Project operator is performed on that single table.)
Type of JOIN: Links tables using an inequality comparison operator (<, >, ≤, ≥) in the join condition. It is considered to be an extension of natural join.
Theta
_________________ class diagrams are used to represent the static data structures in a data model. The symbols used in the UML class and ER diagrams are very similar. The UML class diagrams can be used to depict data models at the conceptual or implementation abstraction levels.
Unified Modeling Language (UML)
What three (often conflicting) database requirements must be addressed in database design?
a. Design elegance requires that the design must adhere to design rules concerning nulls, derived attributes, redundancies, relationship types, and so on. b. Information requirements are dictated by the end users c. Operational (transaction) speed requirements are also dictated by the end users.
A(n) _____ is an alternate name given to a column or table in any SQL statement.
alias
What are the requirements that two relations must satisfy in order to be considered union-compatible?
both must have the same number of attributes (columns) and corresponding attributes (columns) must have the same domain.
A ______________ attribute is one that can be subdivided to yield meaningful attributes for each of its components.
composite
A ________________ key is one that consists of more than one attribute.
composite
A ______________ attribute is an attribute whose value is calculated (derived) from other attributes.
derived
A field or set of fields in one table that uniquely identifies a tuple of another table
foreign key
According to Codd's _____ rule of relational database, "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)."
logical data independence
______________________ may have many values. For example, a person's education may include a high school diploma, a 2-year college associate degree, a four-year college degree, a Master's degree, a Doctoral degree, and various professional certifications such as a Certified Public Accounting certificate or a Certified Data Processing Certificate.
multi-valued attributes
Failure to understand the distinction between mandatory and optional ____________________ in relationships might yield designs in which awkward (and unnecessary) temporary rows (entity instances) must be created just to accommodate the creation of required entities.
participation
A field in a table which uniquely identifies each record in a database table
primary key
The concept of relationship strength is based on how the _________ of a related entity is defined.
primary key
The Chen notation identifies a weak entity by using a double-walled entity __________.
rectangle
A _____________ relationship exists when an entity is related to itself. For example, a COURSE may be a prerequisite to a COURSE.
recursive
If an employee within an EMPLOYEE entity has a relationship with itself, that relationship is known as a _____ relationship.
recursive
A ___________relationship exists when en entity is existence-dependent on another entity and inherits at least part of its primary key from that entity
strong
A _____ is any key that uniquely identifies each row.
superkey
When the specific cardinalities are not included on the diagram in Crow's Foot notation, cardinality is implied by the use of _____.
symbols
In a database context, a(n) _____ indicates the use of different names to describe the same attribute.
synonym
_____ are especially useful when you are trying to determine what values in related tables cause referential integrity problems.
Outer joins
The Crow's foot symbol with two vertical parallel lines indicates _____ cardinality.
(1, 1)
One characteristic of generalization hierarchies is that they are implemented as ______ relationships.
1:1
The _____ relationship is the "relational model ideal."
1:M
The ___________ relationship is the relational database norm.
1:M
________________ are characteristics of entities.
Attributes
__________________ is the term used in database relations to denote the minimum and maximum number of entity occurrences integrated with one occurrence of the related entity.
Cardinality
Product yields all possible pairs of rows from two tables, also known as the _________ product.
Cartesian
__________ not only helps database designers to stay on track during the design process, it also enables them to pick up the design thread when the time comes to modify the design.
Documentation
In Chen notation, there is no way to represent cardinality. (T/F)
False
In implementation terms, an entity is existence-dependent if it has a mandatory primary key. (T/F)
False
Referential integrity and participation are both bidirectional, meaning that they must be addressed in both directions along a relationship. (T/F)
False
The Crow's Foot notation easily identifies multivalued attributes. (T/F)
False
The Crow's Foot notation is less implementation oriented than the Chen notation. (T/F)
False
The SELECT operator yields a vertical subset of a table. (T/F)
False
The entity relationship model (ERM) is dependent on the database type. (T/F)
False
The order of the rows and columns is important to the DBMS. (T/F)
False
The process of database design is a sequential process. (T/F)
False
The row's range of permissible values is known as its domain. (T/F)
False
Dr. Codd's _____________ rule of relational database states that every value in a table is guaranteed to be accessible through a combination of table name, primary key value, and column name.
Guaranteed Access
______________ are underlined in an ER diagram
Identifiers
_________ is the real power behind the relational database, allowing the use of independent tables linked by common attributes.
JOIN
The conceptual model can handle _____ relationships and multivalued attributes.
M:N
The entity relationship model uses the associative entity to represent a(n) _____ relationship between two or more entities.
M:N
_____ relationships can be implemented by creating a new entity in 1:M relationships with the original entities.
M:N
_____ logic, used extensively in mathematics, provides a framework in which an assertion (statement of fact) can be verified as either true or false.
Predicate
To be considered minimally relational, the DBMS must support the key relational operators _____, PROJECT, and JOIN.
Select
_____, also known as RESTRICT, yields values for all rows found in a table that satisfy a given condition.
Select
A composite identifier is a primary key composed of more than one attribute. (T/F)
True
A data dictionary is sometimes described as "the database designer's database" because it records the design decisions about tables and their structures. (T/F)
True
An entity in the entity relationship model corresponds to a table in the relational environment. (T/F)
True
Connectivities and cardinalities are established by concise statements known as business rules. (T/F)
True
In the Chen and Crow's Foot notations, an entity is represented with a rectangle containing the entity's name. (T/F)
True
In the entity relationship model, a table row corresponds to an entity instance. (T/F)
True
In the original Chen notation, each attribute is represented by an oval with the attribute name connected to an entity rectangle with a line. (T/F)
True
The DIVIDE operation uses one single column table (e.g., column "a") as the divisor and one two column table (e.g., columns "a" and "b") as the dividend. (T/F)
True
Unary relationships are common in manufacturing industries. (T/F)
True
The _____ notation of entity-relationship modelling can be used for both conceptual and implementation modelling.
UML
When two or more tables share the same number of columns, and when their corresponding columns share the same or compatible domains, they are said to be _____ .
Union-Compatible
In a relational table, each column has a specific range of values known as the _____________ domain.
attribute
An index key can have multiple _________________ (a composite index).
attributes
To simplify the conceptual design, most higher-order relationships are decomposed into appropriate equivalent _____ relationships whenever possible.
binary
Another name for a composite entity is a(n) _____ entity.
bridge
A _____ key can be described as a minimal superkey, a superkey without any unnecessary attributes.
candidate
A primary key is a(n) ______________ key chosen to be the primary means by which rows of a table are uniquely identified.
candidate
A relationship _______________ is difficult to establish if only one side of the relationship is known.
classification
The relational operators have the property of ___________ ; that is, the use of relational algebra operators on existing relations (tables) produces new relations.
closure
The entity relationship diagram (ERD) represents the _____ database as viewed by the end user.
conceptual
The first step in building an entity-relationship diagram (ERD) is _____ .
creating a detailed narrative of the organization's description of operations
A derived attribute is indicated in the Chen notation by a _____ that connects the attribute and an entity.
dashed line
A(n) _____________________ provides a detailed description of all tables found within the user/designer-created database.
data dictionary
A relationship ___________ indicates the number of entities or participants associated with a relationship.
degree
A(n) ___________ attribute need not be physically stored within the database.
derived
The decision to store _____ attributes in database tables depends on the processing requirements and the constraints placed on a particular application.
derived
A(n) _____ is the set of possible values for a given attribute.
domain
A relationship is an association between _____.
entities
Knowing the minimum and maximum number of _____ occurrences is very helpful at the application software level.
entity
The 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.
entity
A(n) ____________ links tables on the basis of an equality condition that compares specified columns of each table.
equijoin
A weak entity must be _________ dependent.
existence
To avoid nulls, some designers use special codes, known as ______ , to indicate the absence of some value.
flags
Proper use of ________ keys is crucial to controlling data redundancy
foreign
A _____ is the primary key of one table that has been placed into another table to create a common attribute.
foreign key
In a database context, the word _____ indicates the use of the same attribute name to label different attributes.
homonym
Complex _____ requirements may dictate data transformations, and they may expand the number of entities and attributes within the design.
information
A(n) _____ only returns matched records from the tables that are being joined.
inner join
A(n) ______________ process is based on repetition of processes and procedures.
iterative
In a relational model, _______ are also used to establish relationships among tables and to ensure the integrity of the data.
keys
In the relational model, _____ are important because they are used to ensure that each row in a table is uniquely identifiable.
keys
When indicating cardinality, the first value represents the ________ number of associated entities
minimum
Ideally, an entity identifier is composed of _____ attribute(s).
one
Participation is _____________ if one entity occurrence does not require a corresponding entity occurrence in a particular relationship.
optional
The existence of a(n) _____ entity indicates that its minimum cardinality is zero.
optional
A table is also called a(n) _____________ because the relational model's creator, E. F. Codd, used the two terms as synonyms.
relation
A __________ attribute is an attribute that must have a value.
required
A _____ key is defined as a key that is used strictly for data retrieval purposes.
secondary
A _____ attribute is one that cannot be subdivided.
simple
A person's Social Security number would be an example of a(n) ________________ attribute
single-valued
In Crow's Foot notation, an optional relationship between entities is shown by drawing a(n) on the side of the optional entity.
small circle (o)
When using the Crow's Foot notation, the associative entity is indicated by _____ relationship lines between the parents and the associative entity.
solid
A(n) _____________ relationship is also known as an identifying relationship.
strong
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.
system
The _____ is actually a system-created database whose tables store the user/designer-created database characteristics and contents.
system catalog
A _____ relationship exists when an association is maintained within a single entity.
unary
A(n) _____________ index is an index in which the index key can have only one pointer value (row) associated with it.
unique
Proper data design requires carefully defined and controlled data redundancies to function properly.
warehousing
A _____ entity has a primary key that is partially or totally derived from the parent entity in the relationship.
weak
The existence of a mandatory relationship indicates that the minimum cardinality is 0 or 1 for the mandatory entity. (T/F)
False
The idea of determination is unique to the database environment.
False
