Increase testing & SQL support

I want to write down some ideas about increasing support for commonly used SQL statement.

Some different ideas for doing more testing:

1. Add SQL corpora that should be parsed correctly. I think we can create a directory with multiple dialects with multiple corpora.
Examples can be TPCDS benchmark http://www.tpc.org/tpcds/ and other resources from different projects.
We can test two main things here:
- Whether everything parses to a statement
- When serialized (e.g. to JSON), whether it outputs the same thing as a earlier version of slqparser.
2. Increasing test coverage by adding unit tests
3. Increasing test coverage (not only when measuring coverage by line) by adding property-based tests https://github.com/BurntSushi/quickcheck https://github.com/AltSysrq/proptest
3. Add debug asserts, to make sure any assumptions about the inputs are correct. Because those are enabled during testing, they can be very helpful in general to make sure those really hold.
4. Fuzzing https://github.com/andygrove/sqlparser-rs/pull/211 . This can help with finding any edge cases in the parser which crashes without much effort.

Some great list of general testing strategies can be found here:
https://www.sqlite.org/testing.html

Any feedback, ideas on this?

此 issue 是一项范围较广的提案，涵盖 SQL 语料库、单元测试和基于属性的测试、调试断言以及模糊测试，但没有指定具体的文件或测试。首先查看 parser 当前的测试入口，以及 PR #211 中的模糊测试工作。要视为完成，必须将该提案缩小为一项具体的测试变更，并明确产生 parsing、serialization 或 fuzzing 结果。

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