[FEATURE] Inequality join predicate support

Feature Description

Inequality join predicates are useful in SQL, but do not make sense for parameterisation of HTTP methods. This feature request is for:

• support of inequality join predicates where they make sense (eg: in external SQL backends).
• decent error messaging where they are supplied but disallowed.

Example(s)
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Possible Approaches or Libraries to Consider
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Additional context
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Issue にはファイル、テスト、エントリポイントが特定されていません。まず、join predicate の処理と HTTP メソッドのパラメータ検証を追跡します。対象となる外部 SQL バックエンドで不等号述語が機能し、許可されない使用に対して明確なエラーが返されれば完了です。