Is there a database of somatic copy number alterations (CNAs) in different cancer types? That is, annotations of which CNAs are more commonly seen in different cancer types.
I don't know if there's a database that does exactly what you want, but there are some places that might help you figure this out, especially if you already have a list of CNAs/genes/regions in mind.
ICGC is the first that comes to mind, as it has samples from many types of cancer and copy number data for most of them. Depending on what you want though, you might have to apply for access to download the data you want. It's rather annoying, and their data download tools are atrocious to use, but they have a lot of data.
DGV might be another option, though their data browser is rather dated feeling. They publish a lot of gold-standard germline CNVs and such.
COSMIC is a large database for cancer-associated mutations, including CNVs, so it might be worth a look for you.