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UTA / Science / MSE 3304 / What is a hardware?

What is a hardware?

What is a hardware?

Description

School: University of Texas at Arlington
Department: Science
Course: Database Management Systems
Professor: Karen scott
Term: Spring 2016
Tags: uta database
Cost: 50
Name: Review 1
Description: review
Uploaded: 03/13/2016
7 Pages 6 Views 6 Unlocks
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INSY 3304


What is a hardware?



Midterm Exam Review

∙ Components of a DB System

∙ Hardware

− physical things (ex: computer)

∙ Software

− It contains: operating system software, DBMS, application programs that  access with DBMS(plus utility software for backups)

∙ People

− database designer (who does the design modeling), system and database  admins, systems analysist and programmers, and users

∙ Procedures

− Business rules, the instructions/rules/polices that dictate the design and use of  the system.  

∙ Data

− collection of facts that are stored in your database

∙ Database systems are created and managed at different levels of complexity − Some maybe small/ some maybe big (ex. for 1 person or whole industry) ∙ Database solutions must be cost-effective, tactic and strategic Don't forget about the age old question of Who did Rineheart traveled to the Rockies with?

∙ Database technology already in use affects selection of a database system


What are the different types of database systems?



∙ Functions of a DBMS

∙ Transparency

− It should be transparent to the end user which means, it hides the complexity  from the user.

∙ Data dictionary management

− Stores the definitions of data elements and their relationships.  

− DBMS looks up data components structures and relationships. It automatically  records any structural changes in its data dictionary. Also it provides data  abstractions and removes structural and data dependency We also discuss several other topics like How much greater or smaller is the output amplitude compared to the input amplitude?

∙ Data storage management

− Create and manage the data structure that are required for data storage. (ex. create tables, columns)

− Also create data entry forms, reports, screen definitions, query  

definitions…etc.

− Performs fine tuning for you so database perform more efficiently. (ex. create  index)

∙ Data transformation and presentation


What is the process for evaluating and correcting table structures to minimize data redundancy ?



− Transforms from physically to logical and vis-versa. Transforms data to  conform to the required data structures.

∙ Security management

− DBMS creates security system that enforces user’s data security and privacy. ∙ Multiuser access control

− multiple concurrent users

− Takes complex algorithms to maintain the integrity of the data while allowing  for concurrent access. Don't forget about the age old question of What is Polyploidy?

∙ Backup and recovery management

− Backups your data - makes copy of your data and restore if it something is  lost.  

− Backup and data recover to ensure data safety and integrity. Critical to  preserve the integrity of the data

∙ Data integrity management  

− DBMS force and enforce integrity rules. Minimizes redundancy, max  consistency.

− The integrity rules are stored in data dictionary.  

− Referential integrity: Enforces data integrity based on the relationships − Entity integrity: Primary key’s has to be different from once that already exist. ∙ Database access languages and APIs

− SQL is default query language nowadays. SQL is supported by majority of  DBMS vendors. Query languages are non-procedural.  

− API (Application Program Interface): Programs that allow 1 application to  communicate with another application.

∙ Database communication interfaces

− DBMS accepts end-user requests. You can go directly in DBMS and create  different quarries and reports. Also allows you to connect to 3rd party  application We also discuss several other topics like How are there so many different life forms

∙ Different types of database systems (by location and number of users) − You have different vendors for database and you also have different types of  databases.  

∙ Databases classifications

o Number of users

o Database location(s)

o Expected type and extent of use

∙ Number of users

− Single-user database: only one user at a time. (A.K.A. desktop database) − Multi-user database: multiple users using the database at the same time. − Work group database: a department or one small organization (less  than 50 people)

− Enterprise database: multiple department, large companies (over 50 people) If you want to learn more check out What is Gene?

∙ Location

− This is where the data is actually stored.  

− Physical location is where data is stored (ex: in disk or the actual location) − Logical location is how the user sees it.

− You can have a centralized location: all data at a single cite physically at one  spot

− Decentralized location: data is distributed physically at different areas but  logically viewed as single location.

∙ Type and Extent of Use

− Extent (A.K.A. transactional or productional database): operational database  which support the companies day to day operations (ex: payroll, inventory). − Data warehouse and decision support: for tactical or strategic decision making  (ex: see what this company produced in long term and see if they should  continue or not). All the long term data is stored here.  If you want to learn more check out What are the causes of economic growth?

− We can store different data in these databases.

∙ Unstructured

− Unstructured is data that is in its original state.

∙ Structured  

− Structure is data resulting from formatting. (we usually don’t store data like  this)

∙ Semi-structured

− Semi-structured is in between both unstructured and structured. Data  processed to some extent.  

− Ex: some calculated that have total (but we can calculate the total anytime so  why store data in this form?) or if we add “$” to money data (but it is not  necessary to add it and store that data)

∙ XML

− XML is Extensible Markup Language.  

− It represent data elements in textual format.  

− XML format supports semi-structured XML data.(ex: you can use customized  tag like <title><text>)

∙ Basic concepts about the relational database model  

– Entity: Primary key’s has to be different from once that already exist – Attribute: (Property/field). Refers to the initial filing system. Specific characteristic of it.

– Table:

- A.K.A relations.

- Relational model is based on collection of table/relations

- Each table represents an entity.  

- Each table is matrix of rows and columns.

- This model greatly reduced the amount of duplicate data.

– Row: Each row in a table is referred as a tuple

– Column: Each rows and columns intersect and data can be stored in those. – Attribute domain: set of values allowed in an attribute 

∙ Types of keys

– Primary: 1 or more attributes that uniquely identifies each row in a table - Natural: key that is formed of attributes that already exist in the real  world 

- Surrogate: candidate key 

- Entity Integrity: each row can be uniquely identified. Each row much  have a unique identifier. provided by primary keys

− Foreign: 1 or more attributes that value matches the primary key in another table.  1 or more attributes that reference the entire primary key of another table

- Referential Integrity: if a foreign key contains a value, it must refer to an  existing a valid row in a table/relation. Provided by foreign keys

− Super: A key that unique identifies each row. A category of a key. All primary  key, but not all superkey is a primary key.

– Candidate: a super key without unnecessary attributes

– Secondary: used for data retrieval purposes. Don’t have to be unique

∙ Union compatibility: types of columns must match

∙ Relational database operators (definitions and union compatibility requirements) – Union: add the rows together into tables. They must be union compactable (they  must have the same types of columns)

– Intersection: must be union compactable (still same attribute types even if its  named differently). Intersect to see what is in both tables. Yield a result in what  exists in both tables

– Difference: rows of table A – rows of table B. result will yield, whats in 1st table  but not in 2nd table. Have to be union compactable

∙ Product: multiples tables together to get a Cartesian product. Doesn’t have to be  union compactable

∙ Selection: A select retrieves horizontal subset of reference tables. Gives u all the  columns but narrow down the rows

– Projection: yield vertical substance of the table

– Joins :

- Natural join: link the tables together by selecting rows by common values  in their common attributes

- Equijoin: link the tables based on condition of equality, comparing  specific tables

- Theta join: linking tables bases on any comparison operator other than =  sign  

- Outer join: links tables and retains the matched pairs and any un matched  values from 2nd table are left null

– Divide: 2 column table by 1 column table, result will yield any value in the  unmatched column that appears all the values in the 1 column table

∙ Data dictionary

− Provides detailed accounting of all tables found within the user/designer created database

− Contains (at least) all the attribute names and characteristics for each table in  the system

− Contains metadata: data about data

∙ System catalog

− Contains metadata

− Detailed system data dictionary that describes all objects within the database

∙ Data models

– Conceptual: identifies the highest-level relationships between the different  entities. No attributes or primary keys identified. 

– Internal: representation of the database as seen by the DBMS 

– External: Represent the user’s view of the database

– Physical: lowest level of abstractions. This is how the data is stored. ∙ E-R modeling concepts  

– Entities

- Weak: exist when PK of related entity doesn’t contain PK of parent entity 1. it has to be existence dependency

2. PK that is partially or totally derived from PK of parent entity

- Composite:

▪ Also known as bridge entities

▪ Used to implement M:N relationships

▪ Composed of primary keys of each of the entities to be connected ▪ May also contain additional attributes that play no role in  

connective process

– Attributes  

- Simple: can’t be sub divided. Its an atomic in nature

- Composite: it can be sub divided(ex: persons name – 1st name, middle  name, last name)

- single valued: can only have 1 value, even over time it wont change (ex:  DOB)

– Relationships

- Cardinality: Expresses minimum and maximum number of entity  occurrences associated with one occurrence of related entity (ex: credit  hour class: 1,21)

- Connectivity: Describes the relationship classification

- Participation:

▪ Optional: one entity occurrence doesn’t require corresponding  

entity occurrence( dependency)

▪ Mandatory: one entity occurrence requires a corresponding entity  occurrence

- Existence dependency: A semantic control that indicates that an instance  of one entity cannot exist unless an instance of a related entity also exists ∙ Normalization: the process for evaluating and correcting table structures to minimize  data redundancy

∙ Dependencies

– Functional dependency: a constraint that describes the relationship between  attributes in a relation 

– Full functional dependency: full functional dependency occurs when you  already meet the requirements for a functional dependency and the set of  attributes on the left side of the functional dependency statement cannot be  reduced any farther 

– Partial dependency: none key attribute can be determined by part of primary key  (only applies to composite key)

– Transitive dependency: exist when a non-key attribute can be determined by  another non key attribute

∙ Forms of normalization

– 1NF

- Step 1: Eliminate the Repeating Groups  

- Eliminate nulls: each repeating group attribute contains an appropriate  data value

- Step 2: Identify the Primary Key  

- Must uniquely identify attribute value

- New key must be composed

- Step 3: Identify All Dependencies  

- Dependencies are depicted with a diagram

– 2NF

- Step 1: Make New Tables to Eliminate Partial Dependencies

- Write each key component on separate line, then write original  

(composite) key on last line

- Each component will become key in new table

- Step 2: Reassign Corresponding Dependent Attributes  

- Determine attributes that are dependent on other attributes

- At this point, most anomalies have been eliminated

-

– 3NF

- Step 1: Make New Tables to Eliminate Transitive Dependencies  - For every transitive dependency, write its determinant as PK for new table - Determinant: any attribute whose value determines other values within a  row

- Step 2: Reassign Corresponding Dependent Attributes  

- Identify attributes dependent on each determinant identified in Step 1 - Identify dependency

- Name table to reflect its contents and function

∙ Denormalization – what and why?

− Creation of normalized relations is important database design goal − Processing requirements should also be a goal

− If tables are decomposed to conform to normalization requirements: − Number of database tables expands

∙ SQL: Structural Query Lang. default database lang. its non-procedural lang. – DDL: Data Definition Lang (you can definite the structures)

– DML: data manipulation lang. (add, modify, delete, retrieve data) ∙ SQL Statements

– CREATE DATABASE: Create and reserve where the database will be stored – Physical files: that will create a physical files in a disk

– CREATE TABLE: contain the data inside the database

– ALTER TABLE (add columns, delete columns, add constraints) – DROP TABLE: drop table previously stored in the system

– INSERT: Inserts multiple rows from another table

– UPDATE: Modify data in a table

– DELETE: Deletes a table row

– SELECT: Used to list contents of table

– COMMIT: saving to disk. use after inserts, updates or delete – ROLLBACK: undo

∙ Other

– DISTINCT: used in conjunction with SELECT statement to eliminate all the  duplicate records and fetching only unique records. 

– ORDER BY: used to sort the data in ascending or descending order 

Note: Exam will be closed book, closed notes. Questions will be True/False,  Multiple Choice, and Short Answer.

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