WGU C175 Study Notecards

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160 terms MoDhochesPreview WGU C175 Pre-Assessment 50 terms LearningChuPreview WGU C 123 term hay Flat Filesa file having no internal hierarchy Hashed FilesA file that has been encrypted for security purposes.Heap FileAn unsorted set of records.InformationThe transformation of raw data into useful facts.Punch CardA card that is perforated and can hold commands or data.Structured DataInformation with a high degree of organization.Unstructured DataInformation that does not have structure (such as text) Binary RelationshipA relationship between two entity types.Unary RelationshipAn associate occurrence of an entity type with other occurrences of the same entity type.CardinalityThe maximum number of entities that can be involved in a particular relationship.E-R Model *E-R = Entity - Relationship Diagram of entities together with their attributes and the relationship among them.Intersection DataIt is data that describes a many-to-many relationship.

ModalityIt is a minimum number of entity occurrences that can be involved in a relationship.One-to-one Binary RelationshipIt means that a single occurrence of one entity type can be associated with a single occurrence of the other entity type and vice versa.Ternary RelationshipInvolves three different entity types.Unique identifierIt is used to uniquely identify each record in a database table.AttributeA property, characteristic, or fact that we know about an entity."A salesperson works in one office." What is the name of this relationship?One-to-one binary relationship "A salesperson sells to many customers." What is the name of this relationship?One-to-many binary relationship "A salesperson is authorized to sell many products, and a product can be sold by many salespersons." What is the name of this relationship?Many-to-many binary relationship What is the positioning and meaning for Cardinality and Modality on an E-R model?Cardinality is the outer symbol; represents the maximum.Modality is the inner symbol; represents the minimum."A salesperson works in a minimum of one and a maximum of one office, and an office may be occupied by or assigned to a minimum of zero and a maximum of one salesperson." "A salesperson may have no customers or many customers." Describe the ER model for "Each salesperson is authorized to sell to at least one or many products, and each product can be sold by at least one or many salespeople."

"One salesperson backs-up another salesperson." What is the name of this model?One-to-one unary relationship "A salesperson manages zero to many other salespersons, and a salesperson is managed by exactly one other salesperson." What is the name of this model?One-to-many unary relationship "A product can either be part of no other products or be part of several other products, and a product can either be composed of no other products or be composed of several other products." What is the name of this model?Many-to-many unary relationship What does 'refer' in Referential Integrity imply? This revolves around the circumstance of trying to refer to data in one relation in the database, based on values in another relation.Define the delete rule RESTRICT.If the delete rule between two relations is RESTRICT and an attempt is made to delete a record on the "one side" of the one-to-many relationship, the system will forbid the delete to take place if there are any matching foreign key values in the relation on the "many side".Define the delete rule CASCADE.If the delete rule between two relations is CASCADE and an attempt is made to delete a record on the "one side" of the relationship, not only will the record be deleted but all of the records on the "many side" of the relationship that have a matching foreign key value will also be deleted.In other words, the delete will "cascade" from one relation to the other.Define the delete rule SET-TO-NULL.If the delete rule between the two relations is SET-TO-NULL and an attempt is made to delete a record on the "one side" of the one-to-many relationship, that record will be deleted and the matching foreign key values in the records on the "many side" of the relationship will be set to null.Essentially, it's exactly like the CASCADE delete option, but instead of completely deleting all possible values, the values are set to NULL instead.Which entity is uniquely identified by concatenating the primary keys of the two entities it connects?Associative Entity Which type of entity is also called a dependent entity? Weak Entity Candidate KeyThis is when a relation has more than one attribute or minimum group of attributes that represents a way of uniquely identifying the entity.Concurrency ProblemWhen two or more users are trying to update the same record simultaneously.

EquijoinCombines two or more tables based on a column that is common to the tables.

Example: Joining Client and Salesman tables that both contain the SalesmanID

column which have the exact same values.Foreign KeyWhen an attribute or group of attributes serves as the primary key of one relation and also appears in another relation.Natural JoinMatches each row in a table against each row in another table based on common values found in columns sharing a common name and data type.TupleRows/records are referred to as tuples when talking about relations. They serve the exact same function, it just has a different name in the context of relations.What are the five basic principles of The Database Concept?

• The creation of a datacentric environment that is a significant company resource,

which can be shared inside and outside the company.

• The ability to achieve data integration while storing data in a non-redundant

fashion.

• The ability to store data representing entities involved in multiple relationships

w/o introducing data redundancy.

• Managing data control issues such as data security, backup and recovery, and

concurrency control.

• High degree of data independence.

What are the four major DBMS approaches?- Hierarchical

• Network
• Relational
• Object-oriented

What are four key differences between a RELATION and a FILE?

• The columns of a relation can be arranged in any order w/o affecting the

meaning of the data. That is not true of a file.

• Similarly, the rows of a relation can be arranged in any order, which is not true of

a file.

• Every row/column position, sometimes referred to as a "cell", can have only a

single value, which is not necessarily true in a file.

• No two rows of a relation are identical, which is not necessarily true in a file.
• in the SELECT clause- It indicates that all attributes of the selected row are to be retrieved

AND operator- It displays a record if more than one condition is true AVG() function- It returns the average value of a numeric column.BETWEEN operator- It allows you to specify a range of numeric values in a search.DISTINCT operator- It is used to eliminate duplicate rows in a query result.IN operator- It allows you to specify a list of character strings to be included in a search JOIN clause- It is used to combine rows from more than one table, based on a common field between them. Sometimes it is done by using the '=' symbol.