Load the data into SpatiaLite in QGIS... best way is to create a new SpatiaLite database via the right-click GUI in the browser window, then simply drag and drop your shapefile onto the SpatiaLite database you just created. From there you have all the power of SpatiaLite at your disposal.

Some more documentation can be found here, and there's the SpatiaLite manager plugin.

Load the data into SpatiaLite in QGIS... best way is to create a new SpatiaLite database via the right-click GUI in the browser window, then simply drag and drop your shapefile onto the SpatiaLite database you just created. 

From there you have all the power of SpatiaLite at your disposal, including SQL and SQL Spatial functions, which are a way more intuitive way to work with this kind of data.

Some more documentation can be found here, and there's the SpatiaLite manager plugin.