sql: add a special keywords section

[shichun-0415]

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What is changed, added or deleted? (Required)

Close #7982

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What is the related PR or file link(s)?

• This PR is translated from: sql: add a special keywords section docs-cn#13028
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

LGTM

[shichun-0415]

/remove status LGT1
/status LGT2

[shichun-0415]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Details

Commit hash: 0a70eb1

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.4: #12511.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #12512.