diff --git a/application/Espo/Core/Utils/Database/Orm/Relations/Attachments.php b/application/Espo/Core/Utils/Database/Orm/Relations/Attachments.php
index a565f001ca..f60b93ab8e 100644
--- a/application/Espo/Core/Utils/Database/Orm/Relations/Attachments.php
+++ b/application/Espo/Core/Utils/Database/Orm/Relations/Attachments.php
@@ -35,20 +35,29 @@ class Attachments extends HasChildren
     {
         $parentRelation = parent::load($linkName, $entityName);
 
-        $relation = array(
-            $entityName => array (
-                'fields' => array(
-                    $linkName.'Types' => array(
+        $relation = [
+            $entityName => [
+                'fields' => [
+                    $linkName.'Types' => [
                         'type' => 'jsonObject',
                         'notStorable' => true,
-                    ),
-                ),
-            ),
-        );
+                    ],
+                ],
+                'relations' => [
+                    $linkName => [
+                        'conditions' => [
+                            'OR' => [
+                                ['field' => null],
+                                ['field' => $linkName],
+                            ],
+                        ],
+                    ],
+                ],
+            ],
+        ];
 
         $relation = \Espo\Core\Utils\Util::merge($parentRelation, $relation);
 
         return $relation;
     }
 }
-
diff --git a/application/Espo/Core/Utils/FieldManager/Hooks/AttachmentMultipleType.php b/application/Espo/Core/Utils/FieldManager/Hooks/AttachmentMultipleType.php
deleted file mode 100644
index e57770c5b2..0000000000
--- a/application/Espo/Core/Utils/FieldManager/Hooks/AttachmentMultipleType.php
+++ /dev/null
@@ -1,48 +0,0 @@
-<?php
-/************************************************************************
- * This file is part of EspoCRM.
- *
- * EspoCRM - Open Source CRM application.
- * Copyright (C) 2014-2019 Yuri Kuznetsov, Taras Machyshyn, Oleksiy Avramenko
- * Website: https://www.espocrm.com
- *
- * EspoCRM is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * EspoCRM is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with EspoCRM. If not, see http://www.gnu.org/licenses/.
- *
- * The interactive user interfaces in modified source and object code versions
- * of this program must display Appropriate Legal Notices, as required under
- * Section 5 of the GNU General Public License version 3.
- *
- * In accordance with Section 7(b) of the GNU General Public License version 3,
- * these Appropriate Legal Notices must retain the display of the "EspoCRM" word.
- ************************************************************************/
-
-namespace Espo\Core\Utils\FieldManager\Hooks;
-
-use Espo\Core\Exceptions\Conflict;
-
-class AttachmentMultipleType extends Base
-{
-    public function beforeSave($scope, $name, $defs, $options)
-    {
-        if (!empty($options['isNew'])) {
-            $fieldDefs = $this->getMetadata()->get(['entityDefs', $scope, 'fields'], array());
-            foreach ($fieldDefs as $field => $defs) {
-                $type = $this->getMetadata()->get(['entityDefs', $scope, 'fields', $field, 'type']);
-                if ($type === 'attachmentMultiple') {
-                    throw new Conflict("Attachment-Multiple field already exists in '{$scope}'. There can be only one Attachment-Multiple field per entity type.");
-                }
-            }
-        }
-    }
-}
\ No newline at end of file
diff --git a/application/Espo/ORM/DB/Mapper.php b/application/Espo/ORM/DB/Mapper.php
index 12a153438f..51f4f9a9f1 100644
--- a/application/Espo/ORM/DB/Mapper.php
+++ b/application/Espo/ORM/DB/Mapper.php
@@ -232,6 +232,10 @@ abstract class Mapper implements IMapper
                     $params['limit'] = 1;
                 }
 
+                if (!empty($relDefs['conditions']) && is_array($relDefs['conditions'])) {
+                    $params['whereClause'][] = $relDefs['conditions'];
+                }
+
                 $resultArr = [];
 
                 $sql = $this->query->createSelectQuery($relEntity->getEntityType(), $params);
@@ -1005,16 +1009,14 @@ abstract class Mapper implements IMapper
             . " AND "
             . "{$relTable}.deleted = " . $this->pdo->quote(0) . "";
 
+        $conditions = $conditions ?? [];
         if (!empty($relDefs['conditions']) && is_array($relDefs['conditions'])) {
-            foreach ($relDefs['conditions'] as $f => $v) {
-                $join .= " AND {$relTable}." . $this->toDb($f) . " = " . $this->pdo->quote($v);
-            }
+            $conditions = array_merge($conditions, $relDefs['conditions']);
         }
 
-        if (!empty($conditions) && is_array($conditions)) {
-            foreach ($conditions as $f => $v) {
-                $join .= " AND {$relTable}." . $this->toDb($f) . " = " . $this->pdo->quote($v);
-            }
+        if (!empty($conditions)) {
+            $conditionsSql = $this->query->buildJoinConditionsStatement($entity, $relTable, $conditions);
+            $join .= " AND " . $conditionsSql;
         }
 
         return $join;
diff --git a/application/Espo/ORM/DB/Query/Base.php b/application/Espo/ORM/DB/Query/Base.php
index 91b585680f..c10d9c61fd 100644
--- a/application/Espo/ORM/DB/Query/Base.php
+++ b/application/Espo/ORM/DB/Query/Base.php
@@ -1638,10 +1638,41 @@ abstract class Base
         return implode(' ', $joinSqlList);
     }
 
+    public function buildJoinConditionsStatement($entity, $alias = null, array $conditions)
+    {
+        $sql = '';
+
+        $joinSqlList = [];
+        foreach ($conditions as $left => $right) {
+            $joinSqlList[] = $this->buildJoinConditionStatement($entity, $alias, $left, $right);
+        }
+        if (count($joinSqlList)) {
+            $sql .= implode(" AND ", $joinSqlList);
+        }
+
+        return $sql;
+    }
+
     protected function buildJoinConditionStatement($entity, $alias = null, $left, $right)
     {
         $sql = '';
 
+        if (is_array($right) && (is_int($left) || in_array($left, ['AND', 'OR']))) {
+            $logicalOperator = 'AND';
+            if ($left == 'OR') {
+                $logicalOperator = 'OR';
+            }
+
+            $sqlList = [];
+            foreach ($right as $k => $v) {
+                $sqlList[] = $this->buildJoinConditionStatement($entity, $alias, $k, $v);
+            }
+
+            $sql = implode(' ' .$logicalOperator . ' ', $sqlList);
+
+            return $sql;
+        }
+
         $operator = '=';
 
         $isNotValue = false;
@@ -1748,6 +1779,10 @@ abstract class Base
 
         $alias = $this->sanitize($alias);
 
+        if (!empty($relOpt['conditions']) && is_array($relOpt['conditions'])) {
+            $conditions = array_merge($conditions, $relOpt['conditions']);
+        }
+
         $type = $relOpt['type'];
 
         switch ($type) {
@@ -1769,10 +1804,6 @@ abstract class Base
                     . " AND "
                     . "{$midAlias}.deleted = " . $this->pdo->quote(0);
 
-                if (!empty($relOpt['conditions']) && is_array($relOpt['conditions'])) {
-                    $conditions = array_merge($conditions, $relOpt['conditions']);
-                }
-
                 $joinSqlList = [];
                 foreach ($conditions as $left => $right) {
                     $joinSqlList[] = $this->buildJoinConditionStatement($entity, $midAlias, $left, $right);
@@ -1797,7 +1828,6 @@ abstract class Base
                     . " AND "
                     . "{$alias}.deleted = " . $this->pdo->quote(0) . "";
 
-
                 $joinSqlList = [];
                 foreach ($conditions as $left => $right) {
                     $joinSqlList[] = $this->buildJoinConditionStatement($entity, $alias, $left, $right);
diff --git a/tests/unit/Espo/ORM/DB/QueryTest.php b/tests/unit/Espo/ORM/DB/QueryTest.php
index a3faac03da..135fe2ad7f 100644
--- a/tests/unit/Espo/ORM/DB/QueryTest.php
+++ b/tests/unit/Espo/ORM/DB/QueryTest.php
@@ -256,6 +256,24 @@ class QueryTest extends \PHPUnit\Framework\TestCase
         $this->assertEquals($expectedSql, $sql);
     }
 
+    public function testJoinConditions3()
+    {
+        $sql = $this->query->createSelectQuery('Note', [
+            'select' => ['id'],
+            'leftJoins' => [['post', 'post', [
+                'OR' => [
+                    ['name' => 'test'],
+                    ['post.name' => null],
+                ]
+            ]]],
+            'withDeleted' => true,
+        ]);
+
+        $expectedSql = "SELECT note.id AS `id` FROM `note` LEFT JOIN `post` AS `post` ON post.name = 'test' OR post.name IS NULL";
+
+        $this->assertEquals($expectedSql, $sql);
+    }
+
     public function testJoinTable()
     {
         $sql = $this->query->createSelectQuery('Post', [