add example

README.md

@@ -6,4 +6,13 @@ license: odbl
 
 # cBioPortal Datahub
 
-These are parquet files generated from https://github.com/cBioPortal/datahub. It combines all studies' sample, patient, and mutation data into parquet files. They were generated using [cbiohubpy](https://github.com/cBioPortal/cbiohubpy).
+These are parquet files generated from https://github.com/cBioPortal/datahub. It combines all studies' sample, patient, and mutation data into parquet files. They were generated using [cbiohubpy](https://github.com/cBioPortal/cbiohubpy).
+
+## How to use
+
+You can e.g. query the mutations directly like so in `duckdb`:
+
+```
+SELECT count(distinct (Chromosome, Start_Position, End_Position, Reference_Allele, Tumor_Seq_Allele1, Tumor_Seq_Allele2))
+FROM read_parquet('hf://datasets/cBioPortal/datahub/data/combined_mutations.parquet')
+```