Have our own reference pages instead of links.

[mjonss]

Change Request

Please answer the following questions before submitting your issue. Thanks!

1. Describe what you find is inappropriate or missing in the existing docs.
   In the functions-and-operators directory, there are many pages that simply uses a link to dev.mysql.com/doc/refman/... instead of explaining the function/operator in our own documentation. This also causes a dependency on an external resource.

2. Describe your suggestion or addition.
   Create content describing the various functions and operators in TiDB, instead of simply linking to the mysql reference manual.

3. Provide some reference materials (such as documents and websites) if you could.

$  git grep 'dev.mysql.com.*refman' | cut -d: -f1 | uniq -c | sort -n -r
  75 functions-and-operators/operators.md
  62 functions-and-operators/date-and-time-functions.md
  59 functions-and-operators/string-functions.md
  38 functions-and-operators/numeric-functions-and-operators.md
  35 functions-and-operators/json-functions.md
  19 functions-and-operators/miscellaneous-functions.md
  13 functions-and-operators/information-functions.md
  12 functions-and-operators/window-functions.md
  12 functions-and-operators/encryption-and-compression-functions.md
  12 functions-and-operators/aggregate-group-by-functions.md
  11 functions-and-operators/expressions-pushed-down.md
   8 functions-and-operators/bit-functions-and-operators.md

[ran-huang]

Thank you for your suggestion! Independently describing the functions and operators of TiDB rather than linking to the MySQL reference manual would be helpful for our users. Your suggestion is highly appreciated and will be taken into consideration.
However, it is indeed a considerable task, requiring significant manpower and cross-team collaboration. As such, we need to thoroughly assess the impact and timing of such a project. We will consider tackling this project when the appropriate time arises.

[dveeden]

I think this would be useful and I'm available to help with this.

[dveeden]

This is being worked on as part of these:

• Enrich Documentation: TiDB String Functions  #15417
• MySQL 5.7 is still referred to instead of MySQL 8.0 #16809

So we started with directly linking to MySQL docs. Now we have our own descriptions and examples. Eventually we could consider to remove links to the MySQL docs, but that's not something we should do very soon.

The main benefit of this is that we can integrate this more with TiDB specific things like AUTO_RANDOM etc.