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Database 1
Beginning of Database, History/Relational Model/ERD/MySQL
22
Computer Science
Undergraduate 3
10/13/2009

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Cards

Term

Who developed the relational model?

Definition
Edgar Frank Codd
Term

Who developed the Entity-Relationship Diagram?

Definition
P. Chen
Term

What were the predominant database models prior to the relational model?

Definition

network (CODASYL) and hierarchical (IMS)

Term

What are the characteristics of navigational schemes?

Definition

*Calculate Records locations based on file beginning location and record data size
*Read record size from record header and “jump” to next record, until desired record is found

Term
Superkey
Definition
identifies a single row of a table
Term
Candidate Key
Definition
a superkey that has been reduced to the minimal number of cols that still identify unique rows
Term
Primary Key
Definition
the candidate key chosen to be the “first” table key, often becomes the primary index for access table data
Term
Entity Integrity Rule
Definition

§Informal
§Ensures that entities are uniquely identified in the database
§Attributes of Entities are unique
§Formal
§No two rows with the same primary key value
§No NULL values in the primary key

Term
Foreign Key
Definition
column (or set of columns) that matches the candidate key (usually primary key) of another table 
Term
Referential Integrity
Definition

 

§Referential Integrity dictates valid values for a Foreign Key:
§Ensures a database connections are valid
§Values must match a value present in the referenced table
§Null Value

 

Term
Inner Join Operation
Definition

Extracts rows from a product of two tables such that two input rows contributing to any output row satisfy some specified condition.

Term
Outer Join
Definition
Extracts the matching rows (the join part) of two tables and the “unmatched” rows from both tables.
Term
Cross Product
Definition

 

Builds a table consisting of all combinations of rows from each of the two input tables

 

Term
Weak Entities / Identifying Relationships
Definition

 

Weak entities have the PK of a strong entity as part/all of their PK
Solid Relationship line for identifying relationships
Diagonal lines in the corner denote weak entities.

 

Term

 

Optional, Mandatory, Functional

 

Definition

Minimum cardinality >=1

Optional = Minimum Cardinality = 0

Functional = Maximum Cardinality = 1

Term

 

Generalization Hierarchy

 

Definition

 

Subtypes inherit attributes of supertypes (direct and indirect).
Allows for different attributes for objects in the same table.

 

Term
Design Phases
Definition

Conceptual Model = ERD

Logical Design = Relational Database Tables

Distributed Database = Distribution Schema

Physical Database = Internal Schema/Populate

Term
Generalization Constraints
Definition

Disjointness Constrain:Cannot have more than one sub-type.

Completeness Constrain: Must have at least one sub-type.

Term
Procedural vs Non-Procedural
Definition
Procedural language determines WHAT & HOW a process should be done, Non-procedural language is concerned with the WHAT not the HOW. Non-proc languages are those languages where you specify what conditions the answer should satisfy, but not how to obtain it.
Term
Importance of Relational Model
Definition

*No longer did we need to know how the information was formatted in order to get the data.

*Every data item had a unique key or one way to get that item that no other item had.

 

Term
Characteristics of Primary Key
Definition

 

§Stable: never change after assigned
§Single purpose: no other purpose
§Good choices: automatically generated values
§Compromise choice for industry practices
§Identify other unique attributes
Term
SELECT Statement Overview
Definition

 

SELECT <list of column expressions>

 FROM <list of tables and join operations>

 WHERE <list of logical expressions for rows>

 GROUP BY <list of grouping columns>

 HAVING <list of logical expressions for groups>

 ORDER BY <list of sorting specifications>

 

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