1. Geog. 314
Working with tables

2. Introduction GIS involves both spatial and attribute data
Spatial data is concerned with the geometry (position & shape) of map feature
Attribute data describe a characteristic of map feature (colour, name, size, type, etc)
Attribute data are stored in tables

3. Introduction Two types of vector data models:
Georelational data model (dominant in GIS) stores spatial and attribute data separately and links them using the feature ID. Before any analysis can be performed , you must synchronize the two datasets
Object oriented data model combines the spatial and attribute data in a single database. Here each map feature has a unique object ID and an attribute to store its geometry.

4. Tables & Attribute data
Tabular information is the basis of geographic features. They allow you to perform the following tasks:
visualize
Query
analyze your data

5. Organization of Attribute data
tables are made up of rows and columns, and all rows have the same number of columns
Each row of a table represents a map feature
Each column represent a characteristic

6. Organization of Attribute data
rows are known as records or tuples
columns are fields or items
Each field can store a specific type of data, such as a number, date, or piece of text, etc
Attribute tables are called feature attribute tables (point attribute table (PAT), arc attribute table (AAT), polygon attribute table (PAT)

7. Organization of Attribute data
Attribute data are managed using DBMS
A database management systems (DBMS) is a set of computer programs for managing an integrated and shared database (Laurini and Thompson, 1992)
DBMS provide tools for data input, search, retrieval, manipulation, and ouput

8. Types of attribute data
We can classify attribute data by (data type & measurement scale
Data type
- character or string, number (integer, float, double), date, etc
Measurement scale
- categorical (nominal &ordinal) and numeric (ratio & interval)
relationship between measurement scale and data type
- ordinal and nominal – character strings
- interval & ratio – integer and real numbers

9. data types
Numbers: Can be one of four numeric data types: short integers, long integers, single-precision floating-point numbers (often referred to as floats) and double-precision floating-point numbers (commonly called doubles)
Text or string: for storing textual or alphanumeric data
Date: storing date and time
BLOB: Object linking and embedding (OLE) objects are objects created in other applications that are linked or embedded in Access. In this case, binary large object (BLOB) and GEOMETRY data types don't exist in Access, so the object is in ArcGIS and linked to the Access database.

10. Numeric data types Short integer
Stores numbers between -32,768 to 32,767
Size on hard disk: 2bytes
Applications: Numeric values without fractional values within specific range; coded values

11. Numeric data types Long integer
Stores number s from -2,147,483,648 to 2,147,483,647
Size on disk: 4bytes
Applications: Numeric values without fractional values within specific range

12. Numeric data types Single-precision floating-point number (float)
Stores numbers approximately from -3.4 X 1038 to 1.2 X 1038
Size on disk: 4bytes
Application: Numeric values with fractional values within specific range

13. Numeric data types Double-precision floating-point number (double)
Stores numbers approximately from -2.2X to 1.8X10308
Size on disk: 8bytes
Application: Numeric values with fractional values within specific range

14. database model
A database is a collection of interrelated tables in digital format.
Four types of databases:
Flat file: contains all data in a large table (e.g. feature attribute table)
Hierarchical: organizes the data at different levels and uses only the one-to-many associations
Network: builds connections across tables
Relational: a collection of tables (also called relations) which can be connected to each other by keys

15. database model PIN Owner Zoning P101 Wang Residential (1) Chang P102
Smith
Commercial (2)
Jones
P103
Costello
P104
a. FLAT FILE
ZONING
b. HIERARCHICAL 1 2
P101
P104
P102
P103
Wang
Chang
Smith
Smith
Jones
Costello

16. database model c. Network Zoning Owner 1 2 Wang Chang Smith Jones
Costello
P101
P102
P103
P104
d. Relational
Zoning
Owner
PIN
Zonecode
P103
N.B: a problem hierarchical and network data model is the linkages b/n tables must be known in advance and built into the computer code

17. Keys of relational databases
Primary keys: represents one or more attributes whose values can uniquely identify a record in a table
Foreign keys: a counterpart of primary key in another table (i.e. the destination table)
In the parcel and zoning tables below, the key to connect the two is zone code.
Note: the key fields may have different names but must be of the same data type and contain the same kind of info.

18. Primary and foreign keys
PIN
Sale Date
Acres
Zonecode
P101
1.0 1
P102
3.0 2
P103
2.5
P104
Primary key
Zonecode
Zoning 1
Residential 2
Commercial
Foreign key