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47 Cards in this Set
- Front
- Back
Benefits of using database systems |
1. data integration and sharing 2. minimal data redundancy 3. cross-functional analysis and reporting |
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Database systems > file-oriented |
Database systems separate physical and logical views. This facilitates developing new applications using a logical view |
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Difference between file-oriented and relational |
File-oriented: more unstructured data store for arbitrary, unrelated data. More general Relational: built on top of the general data storage services provided by file systems |
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Difference between logical and physical view |
Logical: how people conceptually organize and understand the data Physical: how and where data are physically arranged an stored in the computer system. |
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3 types of schemas |
conceptual, external, internal |
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Conceptual-level schema |
organization wide view of entire database listing all data elements and relationships between them |
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External-level schema |
set of individual user views of subschemas |
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Internal-level schema |
provides a low level view of database including descriptions about pointer,s indexes, record lengths, etc |
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Role of accountants in the development of schemas |
involved in conceptual and external levels |
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Data dictionary- def |
the "blueprint" of the structure of the database and includes data elements, field types, programs that use the elements, outputs, etc. |
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How does a DBMS facilitate creating, changing, and querying data |
-creating data through DDL -changing data through DML -querying data through DQL |
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4 DMBS languages- who uses each |
-DDL and DML used by authorized administrators and programmers -DQL and Report writer used by users |
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DDL (data definition language) |
builds the data dictionary, creates the database, describes logical view for users and specifies records or field security constraints |
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DML (data manipulation language) |
changes database content, including data element updates, insertions, and deletions |
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DQL (data query language) |
contains powerful, easy to use commands that enable users to receive, sort, order, and display data |
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Report Writer |
simplifies report creation |
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What sort of info is contained in the data dictionary |
new or deleted data elements and changes in data element names, descriptions, or uses -ex: records containing a specific data item, source of the data item, field type |
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Primary key |
uniquely define a specific row in a table |
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Foreign key |
used to link tables |
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Other nonkey attributes |
store info about that entity |
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2 advantages of semantic data modeling over normalization |
1. facilitates efficient design of transaction processing databases. 2. facilitates communication with system users, which helps ensure the new system meets users' actual needs |
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How does redundancy apply to database design |
Databases store all data in one uniform data which leads to redundancy, which makes fie maintenance time-consuming and error prone |
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Explain the relational database data model |
represents conceptual and external-level schemas as if data are store in tables, in the manner described in the internal-level schema |
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4 basic requirements when logically designing a relational database model |
1. every column in a row must be single valued 2. primary keys cannot be null 3. foreign keys must have values that correspond to the value of the primary key in another table 4. all nonkey attributes must describe a characteristic of the object identified by the primary key |
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What is meant by, "Accountants can and should participate in all stages of the database design process" |
make sure steps are followed properly |
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Describe an REA data model |
-developed specifically for use in designing AIS -provides guidance for database design by identifying what entities should be included and prescribing how to structure relationships |
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Define cardinality |
describe the nature of the relationship between 2 entities by indicating how many instances of one entity can be linked to each specific instance of another entity |
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Steps in developing an REA diagram |
-identify events about which management wants to collect info -identify the resources affected by each event and the agents who participate in those events -determine the cardinalities of each relationship |
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Explain how an AIS system can be viewed as a set of "give-to-get" exchanges |
-events must be linked to at least one resource that they affect -"Get"= increase quantity of inventory and amount of cash -"Give"= decrease quantity of inventory and amount of cash |
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Define min and max cardinalities |
1:1= max cardinality for each entity is 1 1:N= max of 1 entity is 1 and other is many M:N= max for both is many |
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DBMS |
-links the way data are physically stored with each user's logical view of the data -allows users to access, query, or update the database with out reference to how or where data are physically stored |
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Data warehouse |
contains detailed and summarized data for many years and used for analysis |
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Business intelligence |
using a data warehouse for strategic decision making |
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2 types BI |
data mining and OLAP |
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Data mining |
using statistical analysis to discover unhypothesized relationships |
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OLAP |
using queries to guide the investigation of hypothesized relationships |
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Update/insert/delete anomaly |
update- when data values are recorded incorrectly insert- when certain attributes can't be inserted without the presence of other attributes delete- when deleting a row has unintended consequences |
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Two approaches to database design |
normalization and semantic data modeling |
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Normalization |
assumes everything is initially stored in one large table and decomposed into a set of tables |
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3NF |
set of tables free of anomalies |
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Database design process (5 steps) |
1. system analysis 2. conceptual design 3. physical design 4. implementation and conversion 5. operation and maintenance |
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ER diagrams |
-graphical technique for portraying a database schema - shows the various entities being modeled and the important relationships among them |
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"R" |
resources- have economic value to the organization ex: cash, inventory |
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"E" |
events- various business activities that management wants to collect info on ex: sales, purchases, payroll, receive/disburse cash |
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"A" |
agents- people and organizations that participate in events about whom info is desired for planning, control, and evaluation purposes ex: employees, customers, suppliers |
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A well-structured relational database |
every tables must be related to at least one other table |
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What stage of the database design process is data modeling |
system analysis, conceptual design, physical design |