How to apply a filter
* Right-click on the layer listed in panel Layers
* Choose Filter...
* The window Query Builder is displayed
How to build a query in Query Builder
* Double click on a field in Fields list
* Select All in Values
* Choose a operator from Operators
* Double click on a value in Values list
* Your expression is shown at the bottom of the window
* Click Test to have a preview of how many rows are returned
* Click OK to apply the filter
* The layer is displayed according to the filter applied (you see a filter icon aside the layer name in panel Layers)
