Inspired by how much of an improvement the MDC Javascript/DOM docs are over W3Schools, I was looking for a similar wiki comparable to the W3Schools SQL documentation today. I haven’t had much luck.
Is there a wiki documenting all the SQL commands with common-use examples, caveats, and vendor-dependent implementations?
The best documentation usually comes from the source itself. Which documentation you want depends on your RDBMS:
Edit: Based on your updated question, the answer is “What you want does not exist.”