fixed compilation

include/matador/query/column.hpp

@@ -41,6 +41,9 @@ public:
   // ReSharper disable once CppNonExplicitConversionOperator
   operator const std::string&() const; // NOLINT(*-explicit-constructor)
 
+private:
+  static query::table* default_table();
+
 private:
   const query::table* table_{nullptr};
   std::string name_;

include/matador/query/join_data.hpp

@@ -10,7 +10,7 @@
 namespace matador::query {
 
 struct join_data {
-  table* join_table{nullptr};
+  const table* join_table{nullptr};
   std::unique_ptr<abstract_criteria> condition;
 };