SQL data queries using the graphical query builder

The query builder is SQL-like in its language syntax, and it is worth an introduction as part of an independent workflow. For example, simply because I code in Python or write SQL queries doesn’t mean I avoid a good shortcut here and there. Let’s take a look at the query builder and then explore how to integrate SQL syntax into our filters and code expressions.

First, we will access the query builder. Follow these steps:

1. Select Layer from the menu in QGIS, scroll down to Layer Properties, and activate it by clicking on it, as shown in Figure 6.1:

Figure 6.1 – Layer properties in QGIS

2. When you click on the Layer Properties option, the window opens, as shown in Figure 6.2. Select Source and the page will display the following options:
   • Settings: Displays the layer name and data source encoding. The default is UTF-8.
   • Assigned Coordinate Reference System (CRS): This operates...