Download - Database Structure Basics
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Database StructureBasics
National Center for Immunization & Respiratory Diseases
Influenza Division
Pam KennedyAnalyst, McKing Consulting
Regional Training Workshop on Influenza Data Management
Phnom Penh, Cambodia
July 27 – August 2, 2013
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Course Objectives
• Designing a System Function Structure Data Types Data Relationships
• Data Entry Data Standards Forms
• Controls• Control Validation
Data Security
Section 1 Section 2
Questions
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Designing a SystemFunction
• Function of a database is to facilitate the analysis of large amounts of data quickly and efficiently
• Effective databases result from upfront planning before the first data table is built
Who has data /who is collecting data
What data is being collected/needs to be collected
Why is the data needed
When is data collected
Where is data collected
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Designing a System Structure
How many data tables are needed?
How will data be entered?
How will data be stored?
What level of data/database security is needed?
Who needs access to the files?
Will data be used in calculations?
Will regular reports be needed?
Is there a need to export data?
Database structure
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Designing a System Structure
• Database structure
Excel is a ‘flat’ file system
A "flat file" is a plain text or mixed text which usually contains one record per line
There are no structural relationships between the records.
ACCESS is a ‘relational’ system
A relational database matches data by using common characteristics found within the data set. The resulting groups of data are organized and are much easier for many people to understand.
http://en.wikipedia.org/wiki/Flat_file_databasehttp://en.wikipedia.org/wiki/Relational_database
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Designing a System Structure
• Excel and ACCESS both store data in a ‘column/row’ format
• Excel A ‘worksheet’ is the data storage tool
Excel workbook is a collection of worksheets Excel worksheets are ‘flat files’
• ACCESS A ‘table’ is the data storage tool (equivalent to an Excel ‘worksheet’)
Tables relate to other tables forming the basis for data analysis
Tables group like elements together Patient information – name, address, phone, Date of Birth, Site information - site name, site contact info, type of site
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Designing a System Structure
• Worksheets/Tables store data within the database Excel Worksheet
ACCESS Table
Record
Fields Field Value
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Designing a System Data Types
• There are different elements of data: Names, Dates, Cost information, Notes
• Data type is defined during database construction• Excel and ACCESS both have default data types
Excel – ‘general’ ACCESS – ‘text’
• Data type determines how data can be used in calculations Important during analysis or data summary
• Commonly used data types: Excel – general, date, currency ACCESS – text, number, date
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Designing a System Data Types
• Shared data types – Excel and ACCESS Text - for use storing names, short titles, country Number - for use storing numerical data Date/Time - for use storing dates and can capture time Currency - for use storing costs, price, etc.
• ACCESS Specific Data Types Memo - text field without character limit – for use storing notes
In Excel – there is no character limit in any one cell Yes/No - creates check box field in a table (yes = box checked)
AutoNumber – field that assigns an incremental number to each record
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Designing a SystemData Types
• Excel
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Designing a System Data Types
• ACCESS
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Designing a System Data Relationships
• ACCESS Specific
• What is a relational database ?
System that links data by using common characteristics
System that stores data in logical manner making analysis easier
Provide more efficient means of dealing with duplicated data
• An ACCESS database is composed of the following elements: Tables – Store data Queries – Aid in sorting, summing, calculating data Forms – Aid data input
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Designing a System Data Relationships
• Data relationships are critical
• Relationships should be set up as the database is built
• Questions to consider: How do the fields in different tables relate?
Is there a common factor in all the tables?
• This is the unique field that will apply across all data
Consider data to be collected and how it will be used
Consider data types – relationships link data of same type
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Designing a System Data Relationships
• Key types of relationships One to One – A unique record in Table 1 matches an exact
record in Table 2 One to Many – A unique record in Table 1 matches to several
records in Table 2
SARI Data Table 1
Lab Data Table 2
Patient ID Date of specimen collection
Date of Visit Type of sample collected
Age Sex Results Patient ID
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Example of Data Relationship
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Example of Data Relationship
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Data Entry
• Standards• Forms
Form functions
Controls• Drop down
• Check boxes
• Data Validation
Queries
Data Security
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Data EntryStandards
• Why standardize? Create common understanding Ease comparison of data year to year
Increase efficiency for analyzing Know where data is Know what people are asking for
Everyone enters data in same way
Ease comparison of data from group to group Example
Dateshttp://en.wikipedia.org/wiki/Football
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Data EntryStandards
• Dates
• Football
http://en.wikipedia.org/wiki/Football
12/2/2013 2/12/2013
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Data EntryStandards
• Standards Definition of data types during design phase ensures
standardization of data Numbers stored as numbers Currency stored in specified currency format Dates stored uniformly - ‘Yes’ stored as ‘Yes’ not ‘Y’
‘Controls’ can be used to assist in maintaining data standards Limit data entry choices to defined terms Excel and ACCESS have similar ‘controls’ available
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Data EntryForms
• Building a ‘data entry form’ Identify data fields Determine structure Determine data field relationship (ACCESS) Determine data type for each data field
Dates = date type Cost = currency
Determine common standard responses “Yes” will by stored as ‘Yes’ Choices will be ‘Yes’, ‘No’, ‘NA’ Date format = DDMMYY or DDMMYYYY
• Most of these decisions should be made during database structure design
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Data EntryForms
• Excel
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Data EntryForms
• ACCESS
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Data EntryForms
• Queries Allow you to view, change, and analyze data in different
ways Several types :
Select Parameter Crosstab Action
• A select query is the most common type of query Retrieve data from one or more tables Group records and calculate sums, counts, averages, and
other types of totals
Stefano TEMPIAMicrosoft Access Tutorial – Lecture 2
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Data EntryForms
• Select query
Stefano TEMPIAMicrosoft Access Tutorial – Lecture 2
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Data EntryData Security
• Why security Ensure data is maintained according to set standards Ensure access to data is controlled Ensure accuracy of data
• Security levels Excel
Workbook Worksheet
ACCESS Database Record
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Designing a SystemDatabase Basics
• Questions???
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Designing a SystemDatabase Basics
• Final Thoughts The database should meet your current needs and
any future needs you can anticipate Build a structure that works for you and provides what
you need Be prepared to change and adapt as your data needs
change
Keep it SIMPLE!
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For more information please contact Centers for Disease Control and Prevention1600 Clifton Road NE, Atlanta, GA 30333Telephone, 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348E-mail: [email protected] Web: www.cdc.gov
The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
THANK YOU
National Center for Immunization & Respiratory Diseases
Influenza Division
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Designing a SystemDatabase Basics
• EXERCISESetting up tables using national surveillance forms
Setting up data entry controls
Entering data using controls