SQL语句查询时须要选择主键

select tanhui_xiangmu_carbon.id, sum(carbonStore) from xm_mu_product, xm_user_tree, tanhui_xiangmu_carbon where xm_mu_product.tree_id=xm_user_tree.id and tanhui_xiangmu_carbon.id=xm_user_tree.carbon_i

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