Advanced Accounting Information Systems

Advanced Accounting Information Systems

Day 10 answers

Organizing and Manipulating DataSeptember 16, 2009

AnnouncementsAnnouncements

– Return Quiz 3– Business Week – Free food at noon today– Assignment 2 is posted– Graduate student papers

ObjectivesObjectives

Understand normalization process Understand techniques for validating data inputs Understand the importance of extracting data from

database and AIS uses of such extractions Create simple and multitable queries using Access Understand object-oriented and multimedia databases Be familiar with data warehouses and their uses in

accounting applications

Questions for todayQuestions for today

What are the two methods to design databases?

What are the advantages / disadvantages of each?

If you wanted to use a bottom/up approach to designing a database, which method would you use?

If you wanted to use a top/down approach to designing a database, which method would you use?

Questions for todayQuestions for today

Review first normal form

– Definition

– Examples of concerns

• Data redundancy

• Insertion anomaly

• Deletion anomaly Second normal form

– Definition

– Examples of concerns• Transitive relationship

Third normal form

Question for todayQuestion for today

What is a database management system? – Process of examining and arranging file

data in a way that helps avoid problems when organizations use or modify them later

– Alternative to data modeling concepts such as ERD, organizations may use normalization to organize the data intelligently

Question for todayQuestion for today

Describe the three problems associated with a database in first normal form– Data redundancy– Insertion anomaly– Deletion anomaly

Question for todayQuestion for today

What is a data warehouse?

What is wrong with flat files?What is wrong with flat files?

Flat files – files with no sequence or order to them – student grades of an examination in random order– Almost impossible to

• find a particular record easily (because records are not stored systematically),

• link files to one another to provide information from related records

• store file data efficiently

Three levels of normalization we will look atThree levels of normalization we will look at

First normal form Second normal form Third normal form

First normal form (INF)First normal form (INF)

All record’s attributes (data fields) are well defined and information can be stored as a flat file – compare Figure 14.1 to 14.2

Problems remain– Data redundancy– Insertion anomaly– Deletion anomaly

Second normal form (2NF)Second normal form (2NF)

Database is in first normal form and all the data items in each record depend on the record’s primary key

Problem remain– Field A determines value in field B

Third normal form (3NF)Third normal form (3NF)

Database is in second normal form and contains no transitive dependencies (i.e. no relationships where data field A determines data field B)

Actions available with 3NF– Avoids insertion anomaly– Avoids deletion anomaly

DBMSDBMS

Software system that allows users to create database records, delete records, access specific information, select (query) records for viewing or analysis, alter database information, reorganize records as needed

Not a database Examples – Access, dBASE, paradox, FoxPro,

DB2 , Oracle, Sybase, SQL Server

Data ValidationData Validation

DDL of DBMS– Enables users to define the record structure of any particular database table

– Validation techniques

• Proper data types for fields

• Input masks – telephone numbers, ssn, date

• Default values – 40 hours per week

• Validation rules – between 1 to 100

• Referential integrity –

Cascade update –

Cascade downward

Extracting Data from Databases: Data Manipulation LanguagesExtracting Data from Databases: Data Manipulation Languages

Schema– Map or plan of the entire database

Subschema– Subset of information in database – designed to meet user

needs Queries

– Allow database developers to create customized subschemas Dynaset

– Dynamic subset of a database that you create with such queries

Creating Action QueriesCreating Action Queries

Update queries– Allows user to alter selected table records systematically

Append queries– Allow user to append records from one table to the end of

another table Delete queries

– Allow user to delete table records selectively Make-table queries

– Allow user to create a new table from the records that you select in an existing table

Creating Action QueriesCreating Action Queries

Find-duplicate queries– Allows user to find records with duplicate entries in specified

fields Find-unmatched queries

– Allow user to find the records in one table with no matching records in another table

Crosstab queries– Allow user to perform statistical analysis of the data ina table

and provides the cross-tabulation results in a row-and –column format similar to a pivot table in a spreadsheet

Guidelines for Creating QueriesGuidelines for Creating Queries

Spell accurately – look out for Case sensitivity Specify AND and OR correctly Be sure to JOIN tables properly Name queries systematically Choose data fields selectively

Structured Query LanguageStructured Query Language

Select attribute(s) From table(s) Where restrictions

and joins Group by Order by

More complex databasesMore complex databases

Object-oriented

Multi-media

Multidimensional databases

More complex databasesMore complex databases

Data warehouses (enterprise wide systems)– Pool data from separate applications into a large, common

body of information– Useful if data warehouses include

– Advantage

– Need to standardize and scrub (clean) data to ensure uniform accuracy and consistency

– look at restaurant example – p. 462-463 Data marts –

First SQL Practice First SQL Practice

Marcia Felix Corporation – Problem 14.21– Employee table – Figure 14-15

Questions for FridayQuestions for Friday

Identify and describe five basic features of SQL