Q (haiku): How many total studies contain mutation data in the cBioPortal database?

▶ clickhouse_run_select_query
{
 "query": "
SELECT COUNT(DISTINCT cancer_study_identifier) as total_studies_with_mutations
FROM cancer_study
WHERE mutation_sample_count > 0
"
}

◀ result
{"rows":[{"total_studies_with_mutations":542}]}

═ answer (success)
**542 studies** in the cBioPortal database contain mutation data (i.e., have at least one sample profiled for mutations).

This count is based on studies where `mutation_sample_count > 0` in the cancer study metadata table, which tracks the number of samples profiled for somatic mutations across all studies in the portal.