dataX支持表结构不同的多对一，一对多迁移吗？源表能做join操作不

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The issue body is empty and the title only asks about many-to-one and one-to-many migrations between differently structured tables, plus joins on the source table. Start by clarifying the expected source and target relationships, join behavior, and acceptance criteria before locating the relevant DataX entry points. Done should be defined by an agreed supported scenario and verification of its behavior.

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