Database Design StrategiesDatabase Design Strategies

Alinari

Relational Databases

◆ A relational database separates data by subject into different tables that are then related by common fields

◆ A relational database can ensure that your data is easily maintained over time

Relational Databases

✔Eliminates duplicate information✔Eases data entry and maintenance✔Eases data viewing and querying

Benefits of a Relational Database

Tables

◆ A table is the primary structure in a relational database, composed of fields and records

Tables

✔Table Name✔Table Category

– Data– Reference– Cross-Reference

✔Table Description

Important Elements of a Table

Tables

Tables that contain data about more than one subject

Tables that do not have a primary key

Primary Pitfalls to Avoid in Tables

Fields

◆ A field is an attribute, or characteristic, of the subject of the table

Fields

General Elements✔Field Name✔Table Name✔Field Description

Important Elements of a Field

Fields

Table Elements✔Type of Key

– None, Primary, Foreign, Alternate

✔Unique Value✔Required Value✔Data Type

– Boolean, Alphanumeric, Numeric, DateTime, Counter– Valid Characters, Length, Decimal Places

Important Elements of a Field

Fields

Data Entry Elements✔Field Label✔Values Entered By

– User, System

✔ Input Mask✔Display Format✔Default Value

Important Elements of a Field

Fields

Data Validation/Domain Elements✔Range of Allowed Values✔Set of Allowed Values✔Validation Rule

Important Elements of a Field

Fields

Query Elements✔Comparisons Allowed

– =, !=, >, >=, <, <=

✔Operations Allowed– Addition, Subtraction, Multiplication, Division

Important Elements of a Field

Fields

Fields containing multiple valuesRepeating data valuesFields containing calculated values

Primary Pitfalls to Avoid in Fields

Relationships

◆ A relationship is a connection between two tables

◆ A relationship can eliminate duplicate or redundant data

Relationships

✔Parent Table Name✔Child Table Name✔Relationship Type

– One-to-One (1:1)– One-to-Many (1:M)– Many-to-Many (M:M)

Important Elements of a Relationship

Relationships

Not using relationships; or creating all fields in a single table that should be broken into two or more related tables

Primary Pitfalls to Avoid in Relationships

Relationships

Finding one-to-many relationships in your data should signify to you that a relational database is the best choice for your data!In this case, a flat file will not accurately model your data.

Relational Data “Red Flag”

Normalization

◆ Normalization is the process of converting data from a flat file format into a proper relational database

◆ Normalization separates the fields from a large table into multiple, smaller, related tables by removing all unnecessary or duplicate fields

◆ Normalization ensures that each table represents only one subject

Normalization

All data is stored in a single tableA single record contains information on more

than one subjectA single record contains repeating fieldsMultiple records contain the same values for a

group of fields

Signs of a Non-Normalized Table

Normalization

◆ 1NF: Eliminate repeating groups

Normalization

✔Each table is identified with a primary key✔No table contains repeating values

Signs of a Database in First Normal Form

Normalization

◆ 1NF: Eliminate repeating groups◆ 2NF: Eliminate redundant data

Normalization

✔No table contains redundant data; or groups of repeated values for multiple records

Signs of a Database in Second Normal Form

Normalization

◆ 1NF: Eliminate repeating groups◆ 2NF: Eliminate redundant data◆ 3NF: Eliminate columns not dependent on the

key

Normalization

✔Each table contains only fields that are dependent on the primary key; or directly related to the subject of the table

Signs of a Database in Third Normal Form

Database Design Standards

◆ Database standards allow for the development of consistent, well-designed databases– Important for sharing data among multiple users– Important for merging data at a regional level

◆ A user familiar with the standards can open any database developed with those standards and have a good understanding of the tables

Database Design Standards

✔You can easily modify and maintain the structure of your tables and fields

✔You can easily modify the data in your database✔You can easily retrieve and compare information

from your database✔You can easily develop data entry windows and

more robust applications for your database

Advantages of a Well-Designed Database

Naming Standards

✔has a unique descriptive name that is meaningful to the entire organization

✔accurately, clearly, and unambiguously identifies the table subject or field characteristic

✔has the minimum number of words necessary to convey the table subject or field meaning

✔does not contain unknown acronyms or abbreviations

A good table or field name...

Naming Standards

✔does not contains words that describe the physical characteristics, such as “file”, “record”, “data”, or “table”

✔does not identify more than one table subject or field characteristic

✔uses the singular form of the name

A good table or field name...

Naming Standards

Sample EventsSample IDsite id

✔sample_event✔sample_id✔site_id

Poor Choices Better Choices

Avoid Spaces

Naming Standards

Site/Locationsphone #%MossCoverRain?project$

✔site_location✔phone_num✔moss_cover_percent✔ is_raining✔project_cost

Poor Choices Better Choices

Avoid Special Characters

Naming Standards

birddetectionsCLOUDCOVERdwarfsaplingheight

✔bird_detection✔cloud_cover✔dwarf_sapling_height_ft

Poor Choices Better Choices

Separate Words

Naming Standards

DIGITAL_PHOTOSampleStartTimeWindSpeed

✔digital_photo✔sample_start_time✔wind_speed_mph

Poor Choices Better Choices

Use Consistent Case

Naming Standards

life_stagesNumBirdsObserver_Names

✔ life_stage✔bird_count✔observer_name

Poor Choices Better Choices

Singularize Names

Naming Standards

smptrnidWtrCodcol_for_cur

✔sample_transect_id✔water_code✔ is_collected_for_curation

Poor Choices Better Choices

Avoid Unknown Abbreviations

Naming Standards

water_quality_evaluation_code

DescriptionOfGeomorphicDisturbance

smptrnid

✔h2o_quality_eval_code✔geomorphic_disturb_desc✔sample_transect_id

Poor Choices Better Choices

Limit Length

Naming Standards

AmphibianSizetree_sizeTree_Name

✔amphibian_length_in✔ tree_height_m✔ tree_species_name -or-

tree_common_name

Poor Choices Better Choices

Use Specific Names

Naming Standards

full_nameCityStateZipobservers_initials

✔ first_name, last_name✔city_name, state_code,

zip_code✔observer_initials

Poor Choices Better Choices

Ensure Single Values

Naming Standards

total_line_item_costplot_area_m2event_duration_time

✔ item_qty, unit_cost✔plot_width_m,

plot_height_m✔event_start_time,

event_end_time

Poor Choices Better Choices

Avoid Calculations

Naming Standards

avgcountcurrencydatedescexists

Poor Choices

Avoid Reserved Words

groupindexkeymaxmemomin

namenumberorderpercentpropertysection

setsumtimetypevalueyear

Naming a Table

◆ Data table prefix name with tbl_◆ Reference table prefix name with ref_◆ Cross-reference table prefix name with xref_

What category does this table fall into?

What noun or short phrase summarizes the contents of this table?◆ This should adhere to the naming standards

Naming a Table

✔ tbl_site✔ tbl_sample_event✔ ref_park✔ ref_precipitation✔xref_sample_observer

Good Choices

Naming a Field

What noun or short phrase summarizes the contents of this field?◆ This should adhere to the naming standards

What category describes the type of data in this field?

What unit of measure, if any, is required for this field?

Design Strategies Recap

◆ Standards add value to your data◆ Develop naming standards

– Formatting conventions– Naming conventions