1. Chapter 4
Attribute Data

2. References Price, M. (2013). Mastering ArcGIS (6th ed.). McGraw-Hill
Price, M. (2013). Mastering ArcGIS (6th ed.). McGraw-Hill. Mastering ArcGIS, 6/e Instructor Edition Chapter 4: PowerPoint Notes and Figures

3. Outline What is a table? Queries on tables.
Joining and relating tables.
Summary statistics.
Database storage concepts.

4. What is a table?
Data stored as an array of rows and columns, with each row representing an object (feature) and each column representing an attribute (property) of that object.
Field
Title
Records

5. Types of tables Attribute table Standalone table
Stores attributes of map features.
Associated with a spatial data layer.
Has special fields for spatial information.
Standalone table
Stores any tabular data.
Not associated with spatial data.
OID instead of FID.

6. Database Management Systems
Dedicated systems for managing tables of data.
Provide data management for agencies, universities, companies, etc.
Designed for multi-user environments with enhanced security needs.
Focus on data tables with tools for queries, reporting, graphing, etc.

7. Queries on tables.
A query extracts certain records from a table based on a specified condition
How many students have GPA > 3?
How many states have population > 1 million?
How many counties had greater population in 2000 than in 2010?
How many customers have last names beginning with “Mac” or “Mc”?

8. SQL (Structured Query Language )
Many databases use a special query language called Structured Query Language.
Can write queries that work in multiple DBMS environments.
Queries can be saved and reused.
Nearly always case-sensitive.

9. SQL Query Examples Some Valid Queries
SELECT *FROM cities WHERE "POP1990" >=
SELECT *FROM counties WHERE “BEEFCOW_92” < “BEEFCOW_87”
SELECT *FROM parcels WHERE “LU-CODE” = 42 AND “VALUE” > 50000
SELECT *FROM rentals WHERE “RENT” > 700 AND “RENT” < 1500
In most databases, SQL expressions are case-sensitive “Smith” ≠ “SMITH”

10. Query results
The result of a query is a set of selected records that meet the criteria.
Subsequent operations on the table will use only the selected records and ignore the others. A user might…
Export the selected records to a new table,
Calculate statistics on the selected records,
Calculate new values for the selected records, and
Produce a report based on the selected records.

11. Joining and relating tables
Destination table
Source table
Common field
Joined table

12. Join facts
Joins are temporary relationships between tables used by a relational DBMS.
Tables must share a common field (key).
Treats the two tables as a single table.
Original stored data is not affected.
Can be removed when no longer needed.

13. One-to-one joins Destination table Source table
(always imagine on the left)
Source table
(always imagine on the right)
When each record in the destination table matches exactly one record in the source table, we call it a cardinality of one-to-one.

14. Types of Cardinality One-to-one Many-to-one States to Governors
Husbands to wives
Cities to states
Schools to districts

15. ? 3. One-to-many Violates the Rule of Joining
States to cities
Districts to schools
Violates the Rule of Joining
Record to join to destination is ambiguous
Must use a relate instead

16. Relates Similar to a join except that The tables remain separate.
Items selected in one table may be highlighted in the related table

17. Summary statistics
Grouping records in a table according to one categorical field and calculates statistics.

18. Database storage concepts
Database fields typically are defined by
ASCII vs binary type storage
Bytes of storage allocated
Integer vs floating point
Definition limits the values that can be stored
Important to match type to storage requirements
Try to minimize storage space while making sure all potential values will fit in the field
Text (ASCII) field with 10 bytes “Mississipp”
Binary 2-byte signed integer: -32,767 to +32,767
Single-precision floating point x.xxxxxxxeyy

19. ArcGIS field data types