Although styling can represent your data in lots of ways, you may also want to manipulate or query the data itself before applying styling. For example you might want to show on the map only those settlements in the data where the population was greater than 1,000, or where an intervention had been carried out in the last 30 days. Of course you could do this in the source data using a spreadsheet, but this would mean going back to the source data and re-loading the data.
QGIS allows us to apply filters and run queries on the data, so that we can view - and if necessary save - a subset of the data we have loaded.
Create a query which returns only those settlements where the population is greater than 1,000.
Layer > Query to apply a query selection to the data
Fields panel, select a field on which to query - for example
Pop_1, and then use the buttons and the panel below to complete the query
"Pop_1" > 1000
Test to make sure the query will return some rows, then click
OK to run the query against the data