diff --git a/demo/work.cpp b/demo/work.cpp
index aae003d..3140da0 100644
--- a/demo/work.cpp
+++ b/demo/work.cpp
@@ -164,5 +164,58 @@ int main() {
       in( iPT.payload_id, query::query::select({ temp_id_col }).from( temporary ) )
     )
   .str( conn->dialect() );
+
+      // const QString statement = QString( "SELECT %5 FROM %1 "
+      //                                  "LEFT JOIN (SELECT %2, MAX(%3) AS lastSuccessfulLogin FROM %1 WHERE %4 = ? GROUP BY %2) ll "
+      //                                  "ON %1.%2 = ll.%2 "
+      //                                  "WHERE (lastSuccessfulLogin IS NULL OR %3 <= lastSuccessfulLogin) AND %3 < ?" )
+      //                         .arg( LoginHistory::staticSqlMetaInfo().tableName() )
+      //                         .arg( LoginHistory::staticSqlMetaInfo().columnName( LoginHistory::Attributes::userAttributeId() ) )
+      //                         .arg( LoginHistory::staticSqlMetaInfo().columnName( LoginHistory::Attributes::timestampAttributeId() ) )
+      //                         .arg( LoginHistory::staticSqlMetaInfo().columnName( LoginHistory::Attributes::failReasonSqlAttributeId() ) )
+      //                         .arg( LoginHistory::staticSqlMetaInfo().columnName( LoginHistory::Attributes::idAttributeId() ) );
+
+  const auto q = query::query::select({LOGIN_HISTORY.client, query::max(LOGIN_HISTORY.login_time).as( "lastSuccessfulLogin" ) } )
+    .from( LOGIN_HISTORY )
+    .where( LOGIN_HISTORY.fail_reason == _ )
+    .group_by( LOGIN_HISTORY.client );
+    // .as_table("ll");
+
+  const auto stmt3 = query::query::select({ LOGIN_HISTORY.client })
+    .from( LOGIN_HISTORY )
+    .join_left(q/*, "ll"*/ )
+    .on( LOGIN_HISTORY.client == "ll.client" )
+    .where( query::is_null("lastSuccessfulLogin") && LOGIN_HISTORY.login_time < "ll.lastSuccessfulLogin" )
+    .str( conn->dialect() );
+
+  std::cout << stmt1 << std::endl;
+  std::cout << stmt2 << std::endl;
+  std::cout << stmt3 << std::endl;
+
+  // const QString subQuery = QString( "SELECT MAX(%1) AS lastSuccessfulLogin, %3 FROM %2 "
+  //                                 "WHERE(%4 = ? OR %4 = ? OR %4 = ?) AND %3 = ? GROUP BY %3 " );
+  //
+  // const QString statement = QString( "SELECT MAX(t1.%1) AS LAST_FAILED_LOGIN FROM %2 t1 LEFT JOIN"
+  //                                    "(%0) t2 "
+  //                                    "ON t1.%3 = t2.%3 "
+  //                                    "WHERE(t2.lastSuccessfulLogin IS NULL OR t2.lastSuccessfulLogin < t1.%1) "
+  //                                    "AND (t1.%4 = ? OR t1.%4 = ?) "
+  //                                    "AND t1.%3 = ?" )
+  //                           .arg( subQuery )
+  //                           .arg( LoginHistory::staticSqlMetaInfo().columnName( LoginHistory::Attributes::timestampAttributeId() ) )
+  //                           .arg( LoginHistory::staticSqlMetaInfo().tableName() )
+  //                           .arg( columnFilterName )
+  //                           .arg( LoginHistory::staticSqlMetaInfo().columnName( LoginHistory::Attributes::failReasonSqlAttributeId() ) );
+  //
+  // QSqlQuery query( sqlDatabase() );
+  // if ( query.prepare( statement ) ) {
+  //   query.addBindValue( LoginHistory::FailReason::NoFailReason );
+  //   query.addBindValue( LoginHistory::FailReason::NoScenarioForUser );
+  //   query.addBindValue( LoginHistory::FailReason::UserLockedByAdmin );
+  //   query.addBindValue( columnFilterValue );
+  //   query.addBindValue( LoginHistory::FailReason::WrongPassword );
+  //   query.addBindValue( LoginHistory::FailReason::UnknownUserName );
+  //   query.addBindValue( columnFilterValue );
+
   return 0;
 }
\ No newline at end of file
diff --git a/demo/work/admin/LoginHistory.hpp b/demo/work/admin/LoginHistory.hpp
index 0e68ae5..4cd32ed 100644
--- a/demo/work/admin/LoginHistory.hpp
+++ b/demo/work/admin/LoginHistory.hpp
@@ -9,6 +9,8 @@
 
 #include "matador/object/object_ptr.hpp"
 
+#include "matador/query/meta_table_macro.hpp"
+
 #include "matador/utils/base_class.hpp"
 #include "matador/utils/enum_mapper.hpp"
 #include "matador/utils/foreign_attributes.hpp"
@@ -59,6 +61,9 @@ struct LoginHistory : core::Model {
         field::attribute( op, "login_time", login_time );
     }
 };
+
 }
 
+META_TABLE( login_histories, LOGIN_HISTORY, id, version, client, scenario, collection_center, login_name, fail_reason, login_time )
+
 #endif //LOGIN_HISTORY_HPP
diff --git a/demo/work/admin/User.hpp b/demo/work/admin/User.hpp
index ef257ba..9f83748 100644
--- a/demo/work/admin/User.hpp
+++ b/demo/work/admin/User.hpp
@@ -7,6 +7,8 @@
 
 #include "matador/object/object_ptr.hpp"
 
+#include "matador/query/meta_table_macro.hpp"
+
 #include "matador/utils/base_class.hpp"
 #include "matador/utils/foreign_attributes.hpp"
 #include "matador/utils/types.hpp"
@@ -42,4 +44,7 @@ struct User : core::Model {
 };
 
 }
+
+META_TABLE(users, USER, id, version, name, symbol, salt, password, lock_type, locked_at, lock_reason, role, user_directory)
+
 #endif //USER_HPP
diff --git a/include/matador/query/criteria.hpp b/include/matador/query/criteria.hpp
index f58ce6e..eff9286 100644
--- a/include/matador/query/criteria.hpp
+++ b/include/matador/query/criteria.hpp
@@ -3,6 +3,7 @@
 
 #include "matador/query/criteria/between_criteria.hpp"
 #include "matador/query/criteria/binary_criteria.hpp"
+#include "matador/query/criteria/check_null_criteria.hpp"
 #include "matador/query/criteria/collection_criteria.hpp"
 #include "matador/query/criteria/like_criteria.hpp"
 #include "matador/query/criteria/logical_criteria.hpp"
diff --git a/include/matador/query/criteria/check_null_criteria.hpp b/include/matador/query/criteria/check_null_criteria.hpp
new file mode 100644
index 0000000..e66417c
--- /dev/null
+++ b/include/matador/query/criteria/check_null_criteria.hpp
@@ -0,0 +1,26 @@
+#ifndef MATADOR_IS_NULL_CRITERIA_HPP
+#define MATADOR_IS_NULL_CRITERIA_HPP
+
+#include "matador/query/criteria/abstract_column_criteria.hpp"
+
+namespace matador::query {
+enum class check_null_operator {
+  IsNull,
+  IsNotNull,
+};
+
+class check_null_criteria final : public abstract_column_criteria {
+public:
+  check_null_criteria() = delete;
+  check_null_criteria(const table_column& col, check_null_operator op);
+
+  void accept(criteria_visitor& visitor) const override;
+
+  [[nodiscard]] check_null_operator operand() const;
+
+private:
+  check_null_operator operator_{};
+};
+
+}
+#endif  // MATADOR_IS_NULL_CRITERIA_HPP
diff --git a/include/matador/query/criteria/criteria_operators.hpp b/include/matador/query/criteria/criteria_operators.hpp
index f9f6403..9da0479 100644
--- a/include/matador/query/criteria/criteria_operators.hpp
+++ b/include/matador/query/criteria/criteria_operators.hpp
@@ -104,5 +104,8 @@ criteria_ptr between(const table_column &col, utils::placeholder min, utils::pla
 
 criteria_ptr like(const table_column &col, const std::string &pattern);
 
+criteria_ptr is_null(const table_column &col);
+criteria_ptr is_not_null(const table_column &col);
+
 }
 #endif //CRITERIA_CRITERIA_OPERATORS_HPP
\ No newline at end of file
diff --git a/include/matador/query/criteria/criteria_visitor.hpp b/include/matador/query/criteria/criteria_visitor.hpp
index 5b6d00e..e269aed 100644
--- a/include/matador/query/criteria/criteria_visitor.hpp
+++ b/include/matador/query/criteria/criteria_visitor.hpp
@@ -5,6 +5,7 @@ namespace matador::query {
 class between_criteria;
 class binary_criteria;
 class binary_column_criteria;
+class check_null_criteria;
 class like_criteria;
 class logical_criteria;
 class not_criteria;
@@ -18,6 +19,7 @@ public:
     virtual void visit(const between_criteria &node) = 0;
     virtual void visit(const binary_criteria &node) = 0;
     virtual void visit(const binary_column_criteria &node) = 0;
+    virtual void visit(const check_null_criteria &node) = 0;
     virtual void visit(const collection_criteria &node) = 0;
     virtual void visit(const collection_query_criteria &node) = 0;
     virtual void visit(const like_criteria &node) = 0;
diff --git a/include/matador/query/criteria_evaluator.hpp b/include/matador/query/criteria_evaluator.hpp
index 423de59..d2e32ea 100644
--- a/include/matador/query/criteria_evaluator.hpp
+++ b/include/matador/query/criteria_evaluator.hpp
@@ -23,6 +23,7 @@ public:
   void visit(const between_criteria &node) override;
   void visit(const binary_criteria &node) override;
   void visit(const binary_column_criteria &node) override;
+  void visit(const check_null_criteria &node) override;
   void visit(const collection_criteria &node) override;
   void visit(const collection_query_criteria &node) override;
   void visit(const like_criteria &node) override;
diff --git a/include/matador/query/intermediates/query_from_intermediate.hpp b/include/matador/query/intermediates/query_from_intermediate.hpp
index 222457c..6320bc8 100644
--- a/include/matador/query/intermediates/query_from_intermediate.hpp
+++ b/include/matador/query/intermediates/query_from_intermediate.hpp
@@ -16,6 +16,7 @@ public:
   using fetchable_query::fetchable_query;
 
   query_join_intermediate join_left(const table &t);
+  query_join_intermediate join_left(const fetchable_query &q);
   query_from_intermediate join_left(join_data &data);
   query_from_intermediate join_left(std::vector<join_data> &data_vector);
 
diff --git a/include/matador/query/internal/query_parts.hpp b/include/matador/query/internal/query_parts.hpp
index 59fb64e..9bc9d5a 100644
--- a/include/matador/query/internal/query_parts.hpp
+++ b/include/matador/query/internal/query_parts.hpp
@@ -143,10 +143,10 @@ private:
   std::vector<table> tables_;
 };
 
-class query_join_part final : public query_part
+class query_join_table_part final : public query_part
 {
 public:
-  explicit query_join_part(class table tab);
+  explicit query_join_table_part(class table tab);
 
   [[nodiscard]] const class table& table() const;
 
@@ -157,6 +157,20 @@ private:
   class table table_;
 };
 
+class query_join_query_part final : public query_part
+{
+public:
+  explicit query_join_query_part(fetchable_query q);
+
+  [[nodiscard]] const fetchable_query& query() const;
+
+private:
+  void accept(query_part_visitor &visitor) override;
+
+private:
+  fetchable_query query_;
+};
+
 class query_on_part final : public query_part
 {
 public:
diff --git a/include/matador/query/meta_table_macro.hpp b/include/matador/query/meta_table_macro.hpp
index 0b58c03..d5d445d 100644
--- a/include/matador/query/meta_table_macro.hpp
+++ b/include/matador/query/meta_table_macro.hpp
@@ -3,7 +3,6 @@
 
 #include "matador/utils/macro_map.hpp"
 
-#include "matador/query/table_column.hpp"
 #include "matador/query/table.hpp"
 
 #define FIELD(FIELD_NAME) const matador::query::table_column& FIELD_NAME;
diff --git a/include/matador/query/query.hpp b/include/matador/query/query.hpp
index 5f640d6..5595a54 100644
--- a/include/matador/query/query.hpp
+++ b/include/matador/query/query.hpp
@@ -10,10 +10,12 @@ class connection;
 }
 namespace matador::query {
 class schema;
-table_column alias(const std::string &column, const std::string &as);
-table_column alias(table_column &&col, const std::string &as);
 table_column count(const std::string &column);
 table_column count_all();
+table_column sum(const std::string &column);
+table_column avg(const std::string &column);
+table_column max(const std::string &column);
+table_column min(const std::string &column);
 
 class query
 {
diff --git a/include/matador/query/query_builder.hpp b/include/matador/query/query_builder.hpp
index a3134d5..d2e7a54 100644
--- a/include/matador/query/query_builder.hpp
+++ b/include/matador/query/query_builder.hpp
@@ -37,6 +37,7 @@ public:
     void visit( const binary_criteria& node ) override;
     void visit( const binary_column_criteria& node ) override;
     void visit( const collection_criteria& node ) override;
+    void visit( const check_null_criteria& node ) override;
     void visit( const collection_query_criteria& node ) override;
     void visit( const like_criteria& node ) override;
     void visit( const logical_criteria& node ) override;
diff --git a/include/matador/query/query_compiler.hpp b/include/matador/query/query_compiler.hpp
index ec0e814..baa2a9a 100644
--- a/include/matador/query/query_compiler.hpp
+++ b/include/matador/query/query_compiler.hpp
@@ -47,7 +47,8 @@ protected:
 protected:
   void visit(internal::query_select_part &part) override;
   void visit(internal::query_from_part &part) override;
-  void visit(internal::query_join_part &part) override;
+  void visit(internal::query_join_table_part &part) override;
+  void visit(internal::query_join_query_part &part) override;
   void visit(internal::query_on_part &part) override;
   void visit(internal::query_where_part &part) override;
   void visit(internal::query_group_by_part &part) override;
diff --git a/include/matador/query/query_part_visitor.hpp b/include/matador/query/query_part_visitor.hpp
index e0d2bbc..758a763 100644
--- a/include/matador/query/query_part_visitor.hpp
+++ b/include/matador/query/query_part_visitor.hpp
@@ -15,7 +15,8 @@ class query_add_foreign_key_reference_part;
 class query_add_primary_key_constraint_part;
 class query_select_part;
 class query_from_part;
-class query_join_part;
+class query_join_table_part;
+class query_join_query_part;
 class query_on_part;
 class query_where_part;
 class query_group_by_part;
@@ -57,7 +58,8 @@ public:
 
   virtual void visit(internal::query_select_part &part) = 0;
   virtual void visit(internal::query_from_part &part) = 0;
-  virtual void visit(internal::query_join_part &part) = 0;
+  virtual void visit(internal::query_join_table_part &part) = 0;
+  virtual void visit(internal::query_join_query_part &part) = 0;
   virtual void visit(internal::query_on_part &part) = 0;
   virtual void visit(internal::query_where_part &part) = 0;
   virtual void visit(internal::query_group_by_part &part) = 0;
diff --git a/include/matador/query/table_column.hpp b/include/matador/query/table_column.hpp
index 61c37be..c3b37c8 100644
--- a/include/matador/query/table_column.hpp
+++ b/include/matador/query/table_column.hpp
@@ -30,7 +30,7 @@ public:
 
   [[nodiscard]] bool equals(const table_column &x) const;
 
-  table_column as(std::string a);
+  table_column as(const std::string& alias) const;
 
   [[nodiscard]] const std::string& name() const;
   [[nodiscard]] std::string canonical_name() const;
diff --git a/include/matador/sql/dialect.hpp b/include/matador/sql/dialect.hpp
index 7f9ea8a..dcbb26b 100644
--- a/include/matador/sql/dialect.hpp
+++ b/include/matador/sql/dialect.hpp
@@ -152,6 +152,8 @@ public:
   [[nodiscard]] const std::string& in() const;
   [[nodiscard]] const std::string& insert() const;
   [[nodiscard]] const std::string& into() const;
+  [[nodiscard]] const std::string& is_null() const;
+  [[nodiscard]] const std::string& is_not_null() const;
   [[nodiscard]] const std::string& join() const;
   [[nodiscard]] const std::string& like() const;
   [[nodiscard]] const std::string& limit() const;
@@ -218,6 +220,8 @@ private:
     {dialect_token::In,          "IN"},
     {dialect_token::Insert,      "INSERT"},
     {dialect_token::Into,        "INTO"},
+    {dialect_token::IsNull,      "IS NULL"},
+    {dialect_token::IsNotNull,   "IS NOT NULL"},
     {dialect_token::Join,        "LEFT JOIN"},
     {dialect_token::Like,        "LIKE"},
     {dialect_token::Limit,       "LIMIT"},
diff --git a/include/matador/sql/dialect_token.hpp b/include/matador/sql/dialect_token.hpp
index f7e7384..f40a523 100644
--- a/include/matador/sql/dialect_token.hpp
+++ b/include/matador/sql/dialect_token.hpp
@@ -35,6 +35,8 @@ enum class dialect_token : uint8_t {
   In,
   Insert,
   Into,
+  IsNull,
+  IsNotNull,
   Join,
   Like,
   Limit,
diff --git a/source/orm/CMakeLists.txt b/source/orm/CMakeLists.txt
index 462e177..fe0771c 100644
--- a/source/orm/CMakeLists.txt
+++ b/source/orm/CMakeLists.txt
@@ -8,6 +8,7 @@ add_library(matador-orm STATIC
   ../../include/matador/query/criteria/abstract_column_criteria.hpp
   ../../include/matador/query/criteria/abstract_criteria.hpp
   ../../include/matador/query/criteria/between_criteria.hpp
+  ../../include/matador/query/criteria/check_null_criteria.hpp
   ../../include/matador/query/criteria/collection_criteria.hpp
   ../../include/matador/query/criteria/criteria_operators.hpp
   ../../include/matador/query/criteria/criteria_utils.hpp
@@ -102,6 +103,7 @@ add_library(matador-orm STATIC
   query/criteria/abstract_column_criteria.cpp
   query/criteria/between_criteria.cpp
   query/criteria/binary_criteria.cpp
+  query/criteria/check_null_criteria.cpp
   query/criteria/collection_criteria.cpp
   query/criteria/criteria_operators.cpp
   query/criteria/like_criteria.cpp
diff --git a/source/orm/query/criteria/check_null_criteria.cpp b/source/orm/query/criteria/check_null_criteria.cpp
new file mode 100644
index 0000000..30dd5af
--- /dev/null
+++ b/source/orm/query/criteria/check_null_criteria.cpp
@@ -0,0 +1,16 @@
+#include "matador/query/criteria/check_null_criteria.hpp"
+
+#include "matador/query/criteria/criteria_visitor.hpp"
+
+namespace matador::query {
+check_null_criteria::check_null_criteria(const table_column& col, const check_null_operator op)
+: abstract_column_criteria(col)
+, operator_{op} {}
+
+void check_null_criteria::accept(criteria_visitor& visitor) const {
+  visitor.visit(*this);
+}
+check_null_operator check_null_criteria::operand() const {
+  return operator_;
+}
+}  // namespace matador::query
\ No newline at end of file
diff --git a/source/orm/query/criteria/criteria_operators.cpp b/source/orm/query/criteria/criteria_operators.cpp
index 94c45cf..24e9c4f 100644
--- a/source/orm/query/criteria/criteria_operators.cpp
+++ b/source/orm/query/criteria/criteria_operators.cpp
@@ -1,6 +1,7 @@
 #include "matador/query/criteria/criteria_operators.hpp"
 
 #include "matador/query/criteria/between_criteria.hpp"
+#include "matador/query/criteria/check_null_criteria.hpp"
 #include "matador/query/criteria/like_criteria.hpp"
 #include "matador/query/criteria/logical_criteria.hpp"
 #include "matador/query/criteria/not_criteria.hpp"
@@ -118,4 +119,11 @@ criteria_ptr between(const table_column &col, utils::placeholder min, utils::pla
 criteria_ptr like(const table_column &col, const std::string &pattern) {
   return std::make_unique<like_criteria>(col, pattern);
 }
+
+criteria_ptr is_null(const table_column &col) {
+  return std::make_unique<check_null_criteria>(col, check_null_operator::IsNull);
 }
+criteria_ptr is_not_null(const table_column &col) {
+  return std::make_unique<check_null_criteria>(col, check_null_operator::IsNotNull);
+}
+}  // namespace matador::query
diff --git a/source/orm/query/criteria_evaluator.cpp b/source/orm/query/criteria_evaluator.cpp
index 7d8ffd2..0c9dcdb 100644
--- a/source/orm/query/criteria_evaluator.cpp
+++ b/source/orm/query/criteria_evaluator.cpp
@@ -1,18 +1,17 @@
 #include "matador/query/criteria_evaluator.hpp"
 
-#include "matador/query/query_utils.hpp"
 #include "matador/query/criteria/between_criteria.hpp"
 #include "matador/query/criteria/binary_criteria.hpp"
+#include "matador/query/criteria/check_null_criteria.hpp"
 #include "matador/query/criteria/collection_criteria.hpp"
 #include "matador/query/criteria/like_criteria.hpp"
 #include "matador/query/criteria/logical_criteria.hpp"
 #include "matador/query/criteria/not_criteria.hpp"
-
+#include "matador/query/query_utils.hpp"
 #include "matador/sql/dialect.hpp"
 #include "matador/sql/query_context.hpp"
-
-#include "matador/utils/value.hpp"
 #include "matador/utils/enum_mapper.hpp"
+#include "matador/utils/value.hpp"
 
 namespace matador::query {
 namespace detail {
@@ -61,6 +60,14 @@ void criteria_evaluator::visit( const binary_column_criteria& node ) {
   clause_ += prepare_criteria(dialect_, node.left_column()) + " " + detail::BinaryOperatorEnum.to_string(node.operand()) + " " + prepare_criteria(dialect_, node.right_column());
 }
 
+void criteria_evaluator::visit(const check_null_criteria &node) {
+  clause_ += prepare_identifier(dialect_, node.col()) + " ";
+  if (node.operand() == check_null_operator::IsNull)
+    clause_ += dialect_.is_null();
+  else
+    clause_ += dialect_.is_not_null();
+}
+
 void criteria_evaluator::visit(const collection_criteria &node) {
   const auto count = node.values().size();
   for (size_t i = 0; i < count; ++i) {
diff --git a/source/orm/query/intermediates/query_from_intermediate.cpp b/source/orm/query/intermediates/query_from_intermediate.cpp
index 08fd85c..91bed05 100644
--- a/source/orm/query/intermediates/query_from_intermediate.cpp
+++ b/source/orm/query/intermediates/query_from_intermediate.cpp
@@ -10,19 +10,24 @@
 namespace matador::query {
 
 query_join_intermediate query_from_intermediate::join_left(const table &t) {
-  context_->parts.push_back(std::make_unique<internal::query_join_part>(t));
+  context_->parts.push_back(std::make_unique<internal::query_join_table_part>(t));
+  return {context_};
+}
+
+query_join_intermediate query_from_intermediate::join_left(const fetchable_query &q) {
+  context_->parts.push_back(std::make_unique<internal::query_join_query_part>(q));
   return {context_};
 }
 
 query_from_intermediate query_from_intermediate::join_left(join_data &data) {
-  context_->parts.push_back(std::make_unique<internal::query_join_part>(*data.join_table));
+  context_->parts.push_back(std::make_unique<internal::query_join_table_part>(*data.join_table));
   context_->parts.push_back(std::make_unique<internal::query_on_part>(std::move(data.condition)));
   return {context_};
 }
 
 query_from_intermediate query_from_intermediate::join_left(std::vector<join_data> &data_vector) {
   for (auto &[join_table, condition] : data_vector) {
-    context_->parts.push_back(std::make_unique<internal::query_join_part>(*join_table));
+    context_->parts.push_back(std::make_unique<internal::query_join_table_part>(*join_table));
     context_->parts.push_back(std::make_unique<internal::query_on_part>(std::move(condition)));
   }
   return {context_};
diff --git a/source/orm/query/internal/query_parts.cpp b/source/orm/query/internal/query_parts.cpp
index 346571f..3963b1b 100644
--- a/source/orm/query/internal/query_parts.cpp
+++ b/source/orm/query/internal/query_parts.cpp
@@ -147,16 +147,29 @@ void query_from_part::accept(query_part_visitor &visitor) {
   visitor.visit(*this);
 }
 
-query_join_part::query_join_part(class table tab)
+query_join_table_part::query_join_table_part(class table tab)
 : query_part(sql::dialect_token::Join)
 , table_(std::move(tab)) {
 }
 
-const table &query_join_part::table() const {
+const table &query_join_table_part::table() const {
   return table_;
 }
 
-void query_join_part::accept(query_part_visitor &visitor) {
+void query_join_table_part::accept(query_part_visitor &visitor) {
+  visitor.visit(*this);
+}
+
+query_join_query_part::query_join_query_part(fetchable_query q)
+: query_part(sql::dialect_token::Join)
+, query_(std::move(q))
+{}
+
+const fetchable_query &query_join_query_part::query() const {
+  return query_;
+}
+
+void query_join_query_part::accept(query_part_visitor &visitor) {
   visitor.visit(*this);
 }
 
diff --git a/source/orm/query/query.cpp b/source/orm/query/query.cpp
index ae77362..73629ee 100644
--- a/source/orm/query/query.cpp
+++ b/source/orm/query/query.cpp
@@ -2,15 +2,6 @@
 
 namespace matador::query {
 
-table_column alias(const std::string &column, const std::string &as) {
-  return {column, as};
-}
-
-table_column alias(table_column &&col, const std::string &as) {
-  col.as(as);
-  return col;
-}
-
 table_column count(const std::string &column) {
   return {sql::sql_function_t::Count, column};
 }
@@ -18,6 +9,18 @@ table_column count(const std::string &column) {
 table_column count_all() {
   return count("*");
 }
+table_column sum(const std::string& column) {
+  return {sql::sql_function_t::Sum, column};
+}
+table_column avg(const std::string& column) {
+  return {sql::sql_function_t::Avg, column};
+}
+table_column max(const std::string& column) {
+  return {sql::sql_function_t::Max, column};
+}
+table_column min(const std::string& column) {
+  return {sql::sql_function_t::Min, column};
+}
 
 query_create_intermediate query::create()
 {
diff --git a/source/orm/query/query_builder.cpp b/source/orm/query/query_builder.cpp
index 508aaca..9cb0ae2 100644
--- a/source/orm/query/query_builder.cpp
+++ b/source/orm/query/query_builder.cpp
@@ -15,6 +15,10 @@ void criteria_transformer::visit( const binary_criteria& node ) {
 
 void criteria_transformer::visit( const binary_column_criteria& /*node*/ ) {}
 
+void criteria_transformer::visit(const check_null_criteria& node) {
+  update_criteria_column(node);
+}
+
 void criteria_transformer::visit( const collection_criteria& node ) {
   update_criteria_column(node);
 }
diff --git a/source/orm/query/query_compiler.cpp b/source/orm/query/query_compiler.cpp
index 58d374c..7b4ba20 100644
--- a/source/orm/query/query_compiler.cpp
+++ b/source/orm/query/query_compiler.cpp
@@ -174,10 +174,14 @@ void query_compiler::visit(internal::query_from_part &part) {
   }
 }
 
-void query_compiler::visit(internal::query_join_part &part) {
+void query_compiler::visit(internal::query_join_table_part &part) {
   query_.sql += " " + build_table_name(part.token(), *dialect_, part.table());
 }
 
+void query_compiler::visit(internal::query_join_query_part &part) {
+  query_.sql += " " + dialect_->join() + " (" + part.query().str(*dialect_) + ")";
+}
+
 void query_compiler::visit(internal::query_on_part &part) {
   criteria_evaluator evaluator(*dialect_, query_);
   query_.sql += " " + dialect_->on() +
diff --git a/source/orm/query/table_column.cpp b/source/orm/query/table_column.cpp
index e0deed0..adc0111 100644
--- a/source/orm/query/table_column.cpp
+++ b/source/orm/query/table_column.cpp
@@ -91,9 +91,8 @@ bool table_column::equals(const table_column &x) const {
        function_ == x.function_;
 }
 
-table_column table_column::as(std::string a) {
-  alias_ = std::move(a);
-  return {table_, name_, alias_, type_, attributes_, function_};
+table_column table_column::as(const std::string& alias) const {
+  return {table_, name_, alias, type_, attributes_, function_};
 }
 
 const std::string& table_column::name() const {
diff --git a/source/orm/sql/dialect.cpp b/source/orm/sql/dialect.cpp
index 8477457..318b4c2 100644
--- a/source/orm/sql/dialect.cpp
+++ b/source/orm/sql/dialect.cpp
@@ -221,6 +221,14 @@ const std::string &dialect::into() const {
   return token_at(dialect_token::Into);
 }
 
+const std::string &dialect::is_null() const {
+  return token_at(dialect_token::IsNull);
+}
+
+const std::string &dialect::is_not_null() const {
+  return token_at(dialect_token::IsNotNull);
+}
+
 const std::string &dialect::join() const {
   return token_at(dialect_token::Join);
 }