Introduction to ArcGIS forEnvironmental Scientists

Module 2 – Fundamentals

Lecture 6 – Table Functions

6-2 Introduction to ArcGIS

Chapter 6 Objectives

• Table properties and functions

• Field functions

• Graphs and reports

• Cardinality and table relationships

6-3 Introduction to ArcGIS

Structure

Records(rows)

Fields (attributes, columns, items)

• Field names must be unique and start with a letter• Only letters, numbers and underscores are allowed in field names. Aliases may contain other characters

Alias

6-4 Introduction to ArcGIS

Table Characteristics

Layer attribute table Stand-alone table

Relationship to spatial data

One record per feature

None

Object ID and Shape fields required?

Yes Not required, usually not present

Formats GDB, dBase, INFO GDB, dBase, INFO, Excel*, Text*, Access*

*Not editable in ArcGIS

• All tables may be opened in ArcMap or previewed in ArcCatalog

6-5 Introduction to ArcGIS

Table Functions

• Operations that work with the entire table

• Queries

• Change schema or appearance

• Manage relationships

• Create graphs and reports

• Export all or selected records to new table

6-6 Introduction to ArcGIS

Field Functions

• Operations that mostly work with single fields

• Sort (based on up to four fields)

• Summarize by unique values in a field (creates a new table)

• Summary statistics

• Change schema or appearance

• Properties – define alias, set field visibility or make field the Primary Display Field

6-7 Introduction to ArcGIS

Table Relationships

• Datasets with large numbers of attributes are often stored in several tables for management efficiency and ease of use

• Many applications require ancillary data stored in stand-alone tables

• There are two methods to combine tables – joins and relates

• The cardinality, or relationship of how records in different tables match, determines which method is used

6-8 Introduction to ArcGIS

Joins

• One-to-one and many-to-one matches use joins

• For each record, all fields from the matching record in the joined table are appended

• Join is virtual, stored in the map, not on disk

• Joins can be made permanent by exporting to a new table or feature class

• Appended fields can be used to label, symbolize, query or analyze as if they were part of the original table

6-9 Introduction to ArcGIS

1 to 1 Join

6-10 Introduction to ArcGIS

Spatial Joins

• When feature classes do not share attributes, but do share location

• Like table joins, spatial joins work on one-to-one and one-to-many relationships

• Creates a new feature class with attributes from both input feature classes

• Commonly used to add attributes to points from:

– polygons they fall within

– lines or points they are nearest to

6-11 Introduction to ArcGIS

Relates

• One-to-many and many-to-many matches use relates• For each selected record, all matching records in the related

table are selected• To refresh the display of related selections, go to

Options>Related Tables>[Relate Name]

6-12 Introduction to ArcGIS

Many to Many Relate

Reachcode used as key field in both tables

6-13 Introduction to ArcGIS

Graphs and Reports

• Both are created from selected records in a table – if nothing is selected, the entire table is used

• A wizard interface is used to choose graph style (pie, bar, etc.) and report formatting

6-14 Introduction to ArcGIS

Graphs

• May be added to layouts or saved as images

6-15 Introduction to ArcGIS

Reports

• Can be constructed using the built-in ArcMap Report Writer or Crystal Reports

• May be added to layouts, printed or exported to PDF, RTF or text files.