I have a problem with QGIS 3.4.12. As you can see in the image below, it's not possible to execute queries using query builder, because there's always a syntax error. This only happens using this layer ("benigeo"). How can I solve this issue?

I have a problem with QGIS 3.4.12. As you can see in the image below, it's not possible to execute queries using query builder, because there's always a syntax error. This only happens using this layer ("benigeo"). How can I solve this issue?

EDIT: I need to select the list of some attributes, for this reason I don't need a WHERE clause. To be more clear, I attach another screenshot where you can see what I need. In this layer ("waterways") I'm able to SELECT the waterways type list. Instead, in the other layer I have always that error.