Using QGIS 2.16.2, I can successfully select records from a shapefile attribute table using the following expression:
left("start_time", 10) = '2015-08-01'
Please note that start_time is a string field.
However, when I copy and paste the same expression into the shapefile's Layer Properties>General>feature filter>Query Builder I get the following error:
I would expect that the same expression would work everywhere in QGIS. What am I doing wrong?