Book Image

QGIS 2 Cookbook

By : Alex Mandel, Víctor Olaya Ferrero, Anita Graser, Alexander Bruy
Book Image

QGIS 2 Cookbook

By: Alex Mandel, Víctor Olaya Ferrero, Anita Graser, Alexander Bruy

Overview of this book

QGIS is a user-friendly, cross-platform desktop geographic information system used to make maps and analyze spatial data. QGIS allows users to understand, question, interpret, and visualize spatial data in many ways that reveal relationships, patterns, and trends in the form of maps. This book is a collection of simple to advanced techniques that are needed in everyday geospatial work, and shows how to accomplish them with QGIS. You will begin by understanding the different types of data management techniques, as well as how data exploration works. You will then learn how to perform classic vector and raster analysis with QGIS, apart from creating time-based visualizations. Finally, you will learn how to create interactive and visually appealing maps with custom cartography. By the end of this book, you will have all the necessary knowledge to handle spatial data management, exploration, and visualization tasks in QGIS.
Table of Contents (19 chapters)
QGIS 2 Cookbook
About the Authors
About the Reviewers

Joining tables in databases

If you use a database (SpatiaLite or PostGIS) to store your data, vector and nonspatial, then you also have the option of using the database and SQL to perform tables joins. The primary advantages of this method include being able to filter data before loading in the map, perform multitable joins (three or more), and have full control over the details of the join via queries.

Getting ready

You'll need at least two layers in either a SpatiaLite or PostGIS database. These two layers need at least one column in common, and the column in common should contain unique values in at least one table. In this case, our example uses the census_wake_2000 polygon layer and census_wake_2000_pop.csv.

How to do it…

  1. Open the DB Manager plugin that comes with QGIS. You can find this in the Database menu.

  2. Select your database from the tree on the left-hand side, use cookbook.db in SpatiaLite (which was created in Chapter 1, Data Input and Output).


    If you don't see this database listed...