Additional data queries – IS NOT NULL
When working with large datasets, especially OSM files, it makes sense that not every column will have an associated variable. The number of null values can be quite expansive and perhaps you don’t want to include them in your analysis or visualization. Exercising caution when removing missing data is critical but in our case, for example, perhaps we only want data that includes a name for the feature we are exploring.
SQL uses an IS NOT NULL condition that simply returns TRUE when it encounters a non-NULL value; otherwise, it will return FALSE. This is applicable to SELECT, INSERT, UPDATE, or DELETE statements.
In Figure 7.16, we are querying land_area, which returns the name of the land_area specified. We can see that three values or polygons are returned. Let’s take a look at the Geometry Viewer area in Figure 7.17:
Figure 7.16 – IS NOT Null used in multipolygon dataset
When we...
