Relationship between variables

[odow]

You want something like

model = Model()
@variable(model, x[Master.ID])
@variable(model,t[1:length(Relationship.ID)])
for (i, row) in enumerate(eachrow(Relationship))
    for key in values(row)
        if !isempty(key)
            @constraint(model, t[i] == x[key])
        end
    end
end