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Database Structure Basics Pam Kennedy Analyst, McKing Consulting Regional Training Workshop on Influenza Data Management Phnom Penh, Cambodia July 27 – August 2, 2013 National Center for Immunization & Respiratory Diseases Influenza Division Course Objectives Section 1 • Section 2 Designing a System • Data Entry Function Structure Data Types Data Relationships Questions Data Standards Forms • Controls • Control Validation Data Security Designing a System Function • 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 Designing a System Structure Database structure How many data tables are needed? Who needs access to the files? How will data be entered? Will data be used in calculations? How will data be stored? Will regular reports be What level of needed? data/database security is needed? Is there a need to export data? 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_database http://en.wikipedia.org/wiki/Relational_database 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 Designing a System Structure • Worksheets/Tables store data within the database Excel Worksheet ACCESS Table Fields Record Field Value 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 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 Designing a System Data Types • Excel Designing a System Data Types • ACCESS 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 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 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 Example of Data Relationship Example of Data Relationship Data Entry • Standards • Forms Form functions Controls • Drop down • Check boxes • Data Validation Queries Data Security Data Entry Standards • 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 Dates http://en.wikipedia.org/wiki/Football Data Entry Standards • Dates 12/2/2013 2/12/2013 • Football http://en.wikipedia.org/wiki/Football Data Entry Standards • 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 Data Entry Forms • 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 Data Entry Forms • Excel Data Entry Forms • ACCESS Data Entry Forms • 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 TEMPIA Microsoft Access Tutorial – Lecture 2 Data Entry Forms • Select query Stefano TEMPIA Microsoft Access Tutorial – Lecture 2 Data Entry Data 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 Designing a System Database Basics • Questions??? Designing a System Database 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! THANK YOU For more information please contact Centers for Disease Control and Prevention 1600 Clifton Road NE, Atlanta, GA 30333 Telephone, 1-800-CDC-INFO (232-4636)/TTY: 1-888-232-6348 E-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. National Center for Immunization & Respiratory Diseases Influenza Division Designing a System Database Basics • EXERCISE Setting up tables using national surveillance forms Setting up data entry controls Entering data using controls