Import/export by sector/country data source I am looking for import/exports data by sector and country, with partner countries. The goal is to get a picture of overall imports/exports to/from a specific country with (possibly) all of its partners, for any particular sector/year.

So for example: For 2017, oil imports and exports for China with Russia, Angola, Saudi Arabia, etc.
I believe that the UN Comtrade database is the main data source for this kind of query with substantial country coverage.  It's broken down by HS code.

It has its issues.  Reporting is based on national authorities, so you should usually expect data on imports to be more accurate than exports because of the tax implications (so Uganda's imports from Kenya are likely to be more accurate than Kenya's exports to Uganda).