added returning to update statement and added error code implementation for query

include/matador/query/error_code.hpp

@@ -0,0 +1,35 @@
+#ifndef MATADOR_ERROR_CODE_HPP
+#define MATADOR_ERROR_CODE_HPP
+
+#include <cstdint>
+#include <system_error>
+
+namespace matador::query {
+enum class error_code {
+  Success,
+  Failure,
+  InvalidQuery,
+  InvalidSchema,
+  InvalidTable,
+  InvalidColumn,
+  InvalidConstraint,
+  InvalidDataType,
+  InvalidValue
+};
+
+class query_category_impl final : public std::error_category
+{
+public:
+    [[nodiscard]] const char* name() const noexcept override;
+    [[nodiscard]] std::string message(int ev) const override;
+};
+
+const std::error_category& query_category();
+std::error_code make_error_code(error_code e);
+std::error_condition make_error_condition(error_code e);
+
+}
+
+template <>
+struct std::is_error_code_enum<matador::query::error_code> : true_type {};
+#endif //MATADOR_ERROR_CODE_HPP

include/matador/query/intermediates/query_execute_where_intermediate.hpp

@@ -2,6 +2,7 @@
 #define QUERY_EXECUTE_WHERE_INTERMEDIATE_HPP
 
 #include "matador/query/intermediates/executable_query.hpp"
+#include "matador/query/intermediates/fetchable_query.hpp"
 
 namespace matador::query {
 
@@ -14,9 +15,18 @@ class query_execute_where_intermediate : public executable_query
 public:
   using executable_query::executable_query;
 
+  template<typename... TableColumns>
+  fetchable_query returning(const TableColumns&... table_columns) {
+    const std::vector<table_column> tcv { table_columns... };
+    return returning(tcv);
+  }
+
   query_execute_limit_intermediate limit(size_t limit);
   query_execute_order_by_intermediate order_by(const table_column &col);
   query_execute_order_by_intermediate order_by(std::initializer_list<table_column> columns);
+
+private:
+  fetchable_query returning(const std::vector<table_column>& tables);
 };
 
 }

include/matador/query/intermediates/query_into_intermediate.hpp

@@ -2,22 +2,13 @@
 #define QUERY_INTO_INTERMEDIATE_HPP
 
 #include "matador/query/intermediates/executable_query.hpp"
-#include "matador/query/intermediates/fetchable_query.hpp"
+#include "matador/query/intermediates/query_values_intermediate.hpp"
 
 #include "matador/query/value_extractor.hpp"
 
 #include "matador/utils/placeholder.hpp"
 
 namespace matador::query {
-class table_column;
-
-class query_values_intermediate : public executable_query {
-public:
-  using executable_query::executable_query;
-
-  fetchable_query returning(const table_column &col);
-};
-
 class query_into_intermediate : public query_intermediate {
 public:
   using query_intermediate::query_intermediate;

include/matador/query/intermediates/query_set_intermediate.hpp

@@ -9,14 +9,11 @@
 
 namespace matador::query {
 
-class query_set_intermediate : public executable_query
-{
+class query_set_intermediate : public executable_query {
 public:
   using executable_query::executable_query;
 
-  query_execute_where_intermediate where(std::unique_ptr<abstract_criteria> cond) {
-    return where_clause(std::move(cond));
-  }
+  query_execute_where_intermediate where(std::unique_ptr<abstract_criteria> cond);
 
 private:
   query_execute_where_intermediate where_clause(std::unique_ptr<abstract_criteria> &&cond);

include/matador/query/intermediates/query_values_intermediate.hpp

@@ -0,0 +1,24 @@
+#ifndef MATADOR_QUERY_VALUES_INTERMEDIATE_H
+#define MATADOR_QUERY_VALUES_INTERMEDIATE_H
+
+#include "matador/query/intermediates/executable_query.hpp"
+#include "matador/query/intermediates/fetchable_query.hpp"
+
+namespace matador::query {
+class table_column;
+class query_values_intermediate : public executable_query {
+public:
+  using executable_query::executable_query;
+
+  template<typename... TableColumns>
+  fetchable_query returning(const TableColumns&... table_columns) {
+    const std::vector<table_column> tcv { table_columns... };
+    return returning(tcv);
+  }
+
+private:
+  fetchable_query returning(const std::vector<table_column>& tables);
+};
+}
+
+#endif //MATADOR_QUERY_VALUES_INTERMEDIATE_H