Databases Midterm – Flashcards
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What is good decision making?
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Accurate, relevant, timely information.
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Metadata
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data about data; A description of data characteristics and the set of relationships that links the data in a database
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Database structure in a DBMS does what?
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stores a collection of files
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When different versions of the same data appears in different places?
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data inconsistency
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What is a response from a DBMS to a query?
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query result set, "SELECT * FROM CUSTOMER"
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Operational/Transactional database
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Support the day to day operations of a business
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Data Warehouse
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focuses primarily on storing data used to generate information required to make tactical or strategic decisions
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Multiple users over multiple sites or departments
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Enterprise database
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50 or fewer users
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Workgroup database
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desktop database
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Single-user database
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Distributive
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used from different sites, data that's distributed from various sites
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entity
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anything about which data can be collected or stored; A table
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attribute
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characteristic of an entity
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record
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Tuple, row A logically connected set of one or more fields that describes a person, place, or thing.
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Constraint
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places a restriction on a data. Ensures data integrity
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business rules
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serves as a communication tool between users and designers
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A noun is becomes a ...... and a verb becomes a .....
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entity attribute
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When developing a data, allows you to do what?
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see the data logically rather than physically
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Who is the Father of relationship data design or model in 1970 that wrote treaties.
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EF Cod
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What does relation refer to?
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Relation refers to tables, synonymous for table
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What type of logical data has only 0 or 1, true or false?
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Boolean
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Why are keys or identifiers important?
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Key/Identifier uniquely identifies each record/rows. Has to do with the rules of dependency
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What is the converse of A determines B?
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conversely B is functionally dependent on A
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What are the rules of database design?
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*Entity Integrity says that all tables must have a PK and the PK cannot be null. *Referential integrity says that FK must match PK or maybe null depending on business rules.
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What is a Super Key?
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Any key that uniquely identifies a row or record
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What is null?
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Null is unknown or no data?
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What is secondary key is used for and what is an example?
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For retrieval purposes, doesn't indicate uniqueness. Ex. Last name, SSN
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What is a Candidate key?
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A minimal super key no redundant/unnecessary attributes
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What is an ERD?
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Entity relationship design. - conceptual design or database seen by the end user
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How to fix a Multivalued attribute?
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Create a new table, is a one to many relationship.
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What is a domain?
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A set of permissible values.
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Only a ___________ should make up a should make up a key/indenititfer
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single attribute
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Composite Key
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When identifier makes up more than one attribute
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Simple attribute
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Simple attribute cannot be divided any further.
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Single Valued attribute
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an attribute that can have only a single value, *Vin number on car
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Multivalued attribute
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attributes that can have many values house might have more than one phone number
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Derived attribute
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derived from an attribute Doesn't have to be stored Ex, DOB
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Chen model designs
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Using a dashed line, derived attribute in the Chen model n a crows foot, no was to indicate derived attribute
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What is an association between entities?
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relationship
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Strong entity
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*Can exist on it's own and *PK is made up partly or fully derived from parent entity
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Existent Dependent entity
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*Weak relationship* *cannot exist on its own can exist in the database only when it is associated with another related entity occurrence
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Weak Entity vs Existent dependent
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is existent-dependent entity PK is not made up partly or fully derived from parent entity party or fully derived from parent entity
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A(n) ____ database supports a relatively small number of users (usually fewer than 50) or a specific department within an organization.
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workgroup
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The response of the DBMS to a query is the ____.
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query result selt
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A desktop database is a ____ database.
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single user
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A ____ database supports data distributed across several different sites.
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distributed
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A(n) ____ database is used by an organization and supports many users across many departments.
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enterprise
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Business rules are derived from ____.
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a detailed description of an organization's operations
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A(n) ____ is a restriction placed on the data.
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constraint
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____ are important because they help to ensure data integrity.
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Constraints
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A(n) ____ is the equivalent of a field in a file system.
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attribute
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A(n) ____ is anything about which data are to be collected and stored.
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entity
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The relational database model enables you to view data ____ rather than ____
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logically, physically
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The relational model's creator, E. F. Codd, used the term relation as a synonym for ____.
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table
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____ data can have only a true or false (yes or no) values.
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Boolean
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In the relational model, ____ are important because they are used to ensure that each row in a table is uniquely identifiable
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Primary Key
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In the context of a database table, the statement "A ____ B" indicates that if you know the value of attribute A, you can look up the value of attribute B.
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determines
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In an outer join, the matched pairs would be retained and any unmatched values in the other table would be left ____.
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null
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A ____ contains at least all of the attribute names and characteristics for each table in the system.
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data dictionary
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The equijoin takes its name from the comparison operator ____ used in the condition.
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=
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A(n) ____ is an ordered arrangement of keys and pointers.
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index
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Since it is used to link the tables that originally were related in a M:N relationship, the composite entity structure includes—as foreign keys—at least the ____ keys of the parent tables that are to be linked.
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primary
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A derived attribute ____.
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need not be physically stored within the database
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A relationship is an association between ____.
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entities
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A ____ could be a derived attribute.
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person's age
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A(n) ____ might be represented with a single-valued attribute.
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SSN
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A ____ attribute can have only one value.
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single valued
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The Crow's foot symbol with two parallel lines indicates ____ cardinality
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(1,1)
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The associative entity is also known as a ____ entity.
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composite
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A(n) ____ entity is composed of the primary keys of each of the parent entities to be connected.
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associative
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The existence of a(n) ____ relationship indicates that the minimum cardinality is at least 1 for the mandatory entity.
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mandatory
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____ relationships are most common.
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Binary
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Raw facts from which the required information is derived.
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data
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A character or a group of characters (numeric or alphanumeric) that describes a specific characteristic.
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field
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A logically connected set of one or more fields that describes a person, place, event, or thing
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record
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A collection of related records that contain information of interest to the end user
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file
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What is data redundancy, and which characteristics of the file system can lead to it
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Data redundancy exists when unnecessarily duplicated data are found in the database. For example, a customer's telephone number may be found in the customer file, in the sales agent file, and in the invoice file.
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What is data independence?
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data storage characteristics do not affect data access
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What is a DBMS, and what are its functions
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The DBMS stores the definitions of data and their relationships (metadata) in a data dictionary; any changes made are automatically recorded in the data dictionary. The DBMS creates the complex structures required for data storage. The DBMS transforms entered data to conform to the data structures in item
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What is structual independence?
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changing file structure without affecting data access
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Explain the difference between data and information.
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data are raw facts Information is processed data to reveal the meaning behind the facts.
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what is the role of a DBMS, and what are its advantages? What are its disadvantages
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A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database. Advantage: improved decision making Advantage: improved data access
