ODbL (Open Database License)
A copyleft license written for databases rather than for prose or code.
Open Data Commons, a project of the Open Knowledge Foundation, published version 1.0 in 2009. The problem it addresses: individual facts in a database often carry no copyright, while the compilation is protected by the EU database right – which older Creative Commons licenses didn't cover. The ODbL licenses the structure; the contents can sit under a separate license, usually the Database Contents License.
Share-alike applies to derived databases but not to what you produce from them: a rendered map or a chart only needs an attribution notice. OpenStreetMap moved from CC BY-SA 2.0 in 2012, and data from contributors who never accepted the new terms was deleted – a relicensing that cost real map coverage.