Your question was closed because it's not considered a good, on-topic question for this site. There's a lot, a lot, of conversation covering closure over the years, but starting simple, quoting the FAQ:
We feel the best Stack Overflow questions have a bit of source code in them, but if your question generally covers …
- a specific programming problem
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… then you’re in the right place to ask your question!
You appear to be asking for a specification document. That doesn't fit well in any of those categories. Stack Overflow loves to help with programming question, but it doesn't love to be a documentation repository. Your later edit was better, it provided the justification and background ("I did my homework!"), but that's not enough to overcome the non-topicality.
Your question was deleted, in all likelihood, because the three users who voted to delete it didn't think the question was likely to be made suitably on-topic to be answered. It was deleted relatively quickly, but nowhere near record time.
You asked for a copy; here you go.
Where can I find a complete syntax diagram of the SQL standard?
I have searched Google with the phrase "syntax diagram of the SQL standard", which yields either specific implementations (e.g. Oracle, SQLLite) or simplifications. Being relatively new to whitepapers and such, I have found it quite difficult to navigate the technical documentation that I have found over the course of the last couple days of research.
I already understand SQL; what I am really looking for is an offical RFC, etc. that gives enough information to write a parser for the syntax, without pages of verbose explanation to sift through.
The link that Tomek posted is a good start, but it is still quite verbose, is out of date, and I don't understand why it is being hosted by Carnegie Mellon, as opposed to a standards body. The link is http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt
I didn't see anything else in the comments that might have been helpful - you already included Tomek's comment in your edit.