diff --git a/application/Espo/ORM/Query/Part/SelectExpression.php b/application/Espo/ORM/Query/Part/SelectExpression.php
index 53ca8958f0..3359469225 100644
--- a/application/Espo/ORM/Query/Part/SelectExpression.php
+++ b/application/Espo/ORM/Query/Part/SelectExpression.php
@@ -29,7 +29,7 @@
 
 namespace Espo\ORM\Query\Part;
 
-class SelectExpression implements SelectItem
+class SelectExpression
 {
     private $expression;
 
diff --git a/application/Espo/ORM/Query/Part/SelectItem.php b/application/Espo/ORM/Query/Part/SelectItem.php
deleted file mode 100644
index 8e07af9686..0000000000
--- a/application/Espo/ORM/Query/Part/SelectItem.php
+++ /dev/null
@@ -1,37 +0,0 @@
-<?php
-/************************************************************************
- * This file is part of EspoCRM.
- *
- * EspoCRM - Open Source CRM application.
- * Copyright (C) 2014-2021 Yurii Kuznietsov, Taras Machyshyn, Oleksii 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\ORM\Query\Part;
-
-interface SelectItem
-{
-    public function getExpression(): Expression;
-
-    public function getAlias(): ?string;
-}
diff --git a/application/Espo/ORM/Query/Select.php b/application/Espo/ORM/Query/Select.php
index 69765b67d9..2f6417f3dd 100644
--- a/application/Espo/ORM/Query/Select.php
+++ b/application/Espo/ORM/Query/Select.php
@@ -31,7 +31,7 @@ namespace Espo\ORM\Query;
 
 use Espo\ORM\Query\Part\WhereClause;
 use Espo\ORM\Query\Part\SelectExpression as SelectExpr;
-use Espo\ORM\Query\Part\SelectItem;
+use Espo\ORM\Query\Part\SelectExpression;
 
 use RuntimeException;
 
@@ -58,9 +58,9 @@ class Select implements SelectingQuery
     }
 
     /**
-     * Get select items.
+     * Get SELECT items.
      *
-     * @return SelectItem[]
+     * @return SelectExpression[]
      */
     public function getSelect(): array
     {
@@ -82,7 +82,7 @@ class Select implements SelectingQuery
     }
 
     /**
-     * Get order.
+     * Get ORDER items.
      */
     public function getOrder(): array
     {
@@ -90,7 +90,7 @@ class Select implements SelectingQuery
     }
 
     /**
-     * Whether is distinct.
+     * Whether DISTINCT is applied.
      */
     public function isDistinct(): bool
     {
@@ -98,13 +98,16 @@ class Select implements SelectingQuery
     }
 
     /**
-     * Get group by.
+     * Get GROUP BY items.
      */
     public function getGroupBy(): array
     {
         return $this->params['orderBy'] ?? [];
     }
 
+    /**
+     * Get WHERE clause.
+     */
     public function getWhere(): ?WhereClause
     {
         $whereClause = $this->params['whereClause'] ?? null;
diff --git a/application/Espo/ORM/Query/SelectBuilder.php b/application/Espo/ORM/Query/SelectBuilder.php
index 86448a790a..1cd697bb9f 100644
--- a/application/Espo/ORM/Query/SelectBuilder.php
+++ b/application/Espo/ORM/Query/SelectBuilder.php
@@ -30,7 +30,7 @@
 namespace Espo\ORM\Query;
 
 use Espo\ORM\Query\Part\Expression;
-use Espo\ORM\Query\Part\SelectItem;
+use Espo\ORM\Query\Part\SelectExpression;
 
 use InvalidArgumentException;
 use RuntimeException;
@@ -127,23 +127,21 @@ class SelectBuilder implements Builder
     /**
      * Specify SELECT. Columns and expressions to be selected. If not called, then
      * all entity attributes will be selected. Passing an array will reset
-     * previously set items. Passing a string|Expression|SelectItem will append the item.
+     * previously set items. Passing a SelectExpression|Expression|string will append the item.
      *
      * Usage options:
+     * * `select(SelectExpression $expression)`
      * * `select([$expr1, $expr2, ...])`
-     * * `select([[$expr1, $alias1], [$expr2, $alias2], ...])`
-     * * `select([$selectItem1, $selectItem2, ...])`
-     * * `select(string|Expression $expression)`
-     * * `select(string|Expression $expression, string $alias)`
-     * * `select(SelectItem $selectItem)`
+     * * `select(string $expression, string $alias)`
      *
-     * @param array|string|Expression|SelectItem $select An array of expressions or one expression.
-     * @param string|null $alias An alias. Actual if the first parameter is a string.
+     * @param SelectExpression|SelectExpression[]|Expression|string $select
+     * An array of expressions or one expression.
+     * @param string|null $alias An alias. Actual if the first parameter is not an array.
      */
     public function select($select, ?string $alias = null): self
     {
         if (is_array($select)) {
-            $this->params['select'] = $this->normilizeSelectItemArray($select);
+            $this->params['select'] = $this->normilizeSelectExpressionArray($select);
 
             return $this;
         }
@@ -151,7 +149,7 @@ class SelectBuilder implements Builder
         if ($select instanceof Expression) {
             $select = $select->getValue();
         }
-        else if ($select instanceof SelectItem) {
+        else if ($select instanceof SelectExpression) {
             $alias = $alias ?? $select->getAlias();
             $select = $select->getExpression()->getValue();
         }
@@ -271,7 +269,7 @@ class SelectBuilder implements Builder
         return $this;
     }
 
-    private function normilizeSelectItemArray(array $itemList): array
+    private function normilizeSelectExpressionArray(array $itemList): array
     {
         $resultList = [];
 
@@ -282,7 +280,7 @@ class SelectBuilder implements Builder
                 continue;
             }
 
-            if ($item instanceof SelectItem) {
+            if ($item instanceof SelectExpression) {
                 $resultList[] = $item->getAlias() ?
                     [$item->getExpression()->getValue(), $item->getAlias()] :
                     [$item->getExpression()->getValue()];
diff --git a/application/Espo/ORM/QueryBuilder.php b/application/Espo/ORM/QueryBuilder.php
index 7b5916f969..5876a3f6b5 100644
--- a/application/Espo/ORM/QueryBuilder.php
+++ b/application/Espo/ORM/QueryBuilder.php
@@ -38,7 +38,7 @@ use Espo\ORM\{
     Query\Query,
     Query\Builder,
     Query\Part\Expression,
-    Query\Part\SelectItem,
+    Query\Part\SelectExpression,
 };
 
 use ReflectionClass;
@@ -52,18 +52,16 @@ class QueryBuilder
     /**
      * Specify SELECT. Columns and expressions to be selected. If not called, then
      * all entity attributes will be selected. Passing an array will reset
-     * previously set items. Passing a string|Expression|SelectItem will append the item.
+     * previously set items. Passing a SelectExpression|Expression|string will append the item.
      *
      * Usage options:
+     * * `select(SelectExpression $expression)`
      * * `select([$expr1, $expr2, ...])`
-     * * `select([[$expr1, $alias1], [$expr2, $alias2], ...])`
-     * * `select([$selectItem1, $selectItem2, ...])`
-     * * `select(string|Expression $expression)`
-     * * `select(string|Expression $expression, string $alias)`
-     * * `select(SelectItem $selectItem)`
+     * * `select(string $expression, string $alias)`
      *
-     * @param array|string|Expression|SelectItem $select An array of expressions or one expression.
-     * @param string|null $alias An alias. Actual if the first parameter is a string.
+     * @param SelectExpression|SelectExpression[]|Expression|string $select
+     * An array of expressions or one expression.
+     * @param string|null $alias An alias. Actual if the first parameter is not an array.
      */
     public function select($select = null, ?string $alias = null): SelectBuilder
     {
diff --git a/application/Espo/ORM/Repository/RDBRelation.php b/application/Espo/ORM/Repository/RDBRelation.php
index 904b6c9e4d..30b0690456 100644
--- a/application/Espo/ORM/Repository/RDBRelation.php
+++ b/application/Espo/ORM/Repository/RDBRelation.php
@@ -35,7 +35,7 @@ use Espo\ORM\{
     EntityManager,
     Query\Select,
     Query\Part\WhereItem,
-    Query\Part\SelectItem,
+    Query\Part\SelectExpression,
     Mapper\RDBMapper,
     Repository\RDBRelationSelectBuilder as Builder,
 };
@@ -286,18 +286,16 @@ class RDBRelation
     /**
      * Specify SELECT. Columns and expressions to be selected. If not called, then
      * all entity attributes will be selected. Passing an array will reset
-     * previously set items. Passing a string|Expression|SelectItem will append the item.
+     * previously set items. Passing a SelectExpression|Expression|string will append the item.
      *
      * Usage options:
+     * * `select(SelectExpression $expression)`
      * * `select([$expr1, $expr2, ...])`
-     * * `select([[$expr1, $alias1], [$expr2, $alias2], ...])`
-     * * `select([$selectItem1, $selectItem2, ...])`
-     * * `select(string|Expression $expression)`
-     * * `select(string|Expression $expression, string $alias)`
-     * * `select(SelectItem $selectItem)`
+     * * `select(string $expression, string $alias)`
      *
-     * @param array|string|Expression|SelectItem $select An array of expressions or one expression.
-     * @param string|null $alias An alias. Actual if the first parameter is a string.
+     * @param SelectExpression|SelectExpression[]|Expression|string $select
+     * An array of expressions or one expression.
+     * @param string|null $alias An alias. Actual if the first parameter is not an array.
      */
     public function select($select = [], ?string $alias = null): Builder
     {
diff --git a/application/Espo/ORM/Repository/RDBRelationSelectBuilder.php b/application/Espo/ORM/Repository/RDBRelationSelectBuilder.php
index f14f96973c..7fc9d18938 100644
--- a/application/Espo/ORM/Repository/RDBRelationSelectBuilder.php
+++ b/application/Espo/ORM/Repository/RDBRelationSelectBuilder.php
@@ -37,7 +37,7 @@ use Espo\ORM\{
     Query\Select,
     Query\SelectBuilder,
     Query\Part\WhereItem,
-    Query\Part\SelectItem,
+    Query\Part\SelectExpression,
     Mapper\Mapper,
 };
 
@@ -364,18 +364,16 @@ class RDBRelationSelectBuilder
     /**
      * Specify SELECT. Columns and expressions to be selected. If not called, then
      * all entity attributes will be selected. Passing an array will reset
-     * previously set items. Passing a string|Expression|SelectItem will append the item.
+     * previously set items. Passing a SelectExpression|Expression|string will append the item.
      *
      * Usage options:
+     * * `select(SelectExpression $expression)`
      * * `select([$expr1, $expr2, ...])`
-     * * `select([[$expr1, $alias1], [$expr2, $alias2], ...])`
-     * * `select([$selectItem1, $selectItem2, ...])`
-     * * `select(string|Expression $expression)`
-     * * `select(string|Expression $expression, string $alias)`
-     * * `select(SelectItem $selectItem)`
+     * * `select(string $expression, string $alias)`
      *
-     * @param array|string|Expression|SelectItem $select An array of expressions or one expression.
-     * @param string|null $alias An alias. Actual if the first parameter is a string.
+     * @param SelectExpression|SelectExpression[]|Expression|string $select
+     * An array of expressions or one expression.
+     * @param string|null $alias An alias. Actual if the first parameter is not an array.
      */
     public function select($select, ?string $alias = null): self
     {
diff --git a/application/Espo/ORM/Repository/RDBRepository.php b/application/Espo/ORM/Repository/RDBRepository.php
index 48e76bdc19..7aa402cc66 100644
--- a/application/Espo/ORM/Repository/RDBRepository.php
+++ b/application/Espo/ORM/Repository/RDBRepository.php
@@ -38,7 +38,7 @@ use Espo\ORM\{
     Mapper\RDBMapper,
     Query\Select,
     Query\Part\WhereItem,
-    Query\Part\SelectItem,
+    Query\Part\SelectExpression,
 };
 
 use StdClass;
@@ -782,18 +782,16 @@ class RDBRepository extends Repository
     /**
      * Specify SELECT. Columns and expressions to be selected. If not called, then
      * all entity attributes will be selected. Passing an array will reset
-     * previously set items. Passing a string|Expression|SelectItem will append the item.
+     * previously set items. Passing a SelectExpression|Expression|string will append the item.
      *
      * Usage options:
+     * * `select(SelectExpression $expression)`
      * * `select([$expr1, $expr2, ...])`
-     * * `select([[$expr1, $alias1], [$expr2, $alias2], ...])`
-     * * `select([$selectItem1, $selectItem2, ...])`
-     * * `select(string|Expression $expression)`
-     * * `select(string|Expression $expression, string $alias)`
-     * * `select(SelectItem $selectItem)`
+     * * `select(string $expression, string $alias)`
      *
-     * @param array|string|Expression|SelectItem $select An array of expressions or one expression.
-     * @param string|null $alias An alias. Actual if the first parameter is a string.
+     * @param SelectExpression|SelectExpression[]|Expression|string $select
+     * An array of expressions or one expression.
+     * @param string|null $alias An alias. Actual if the first parameter is not an array.
      */
     public function select($select = [], ?string $alias = null): RDBSelectBuilder
     {
diff --git a/application/Espo/ORM/Repository/RDBSelectBuilder.php b/application/Espo/ORM/Repository/RDBSelectBuilder.php
index 6c110fb7cf..22edf18b4f 100644
--- a/application/Espo/ORM/Repository/RDBSelectBuilder.php
+++ b/application/Espo/ORM/Repository/RDBSelectBuilder.php
@@ -37,7 +37,7 @@ use Espo\ORM\{
     Query\Select,
     Query\SelectBuilder,
     Query\Part\WhereItem,
-    Query\Part\SelectItem,
+    Query\Part\SelectExpression,
     Mapper\Mapper,
 };
 
@@ -304,7 +304,7 @@ class RDBSelectBuilder
     /**
      * Specify SELECT. Columns and expressions to be selected. If not called, then
      * all entity attributes will be selected. Passing an array will reset
-     * previously set items. Passing a string|Expression|SelectItem will append the item.
+     * previously set items. Passing a string|Expression|SelectExpression will append the item.
      *
      * Usage options:
      * * `select([$expr1, $expr2, ...])`
@@ -312,9 +312,9 @@ class RDBSelectBuilder
      * * `select([$selectItem1, $selectItem2, ...])`
      * * `select(string|Expression $expression)`
      * * `select(string|Expression $expression, string $alias)`
-     * * `select(SelectItem $selectItem)`
+     * * `select(SelectExpression $selectItem)`
      *
-     * @param array|string|Expression|SelectItem $select An array of expressions or one expression.
+     * @param array|string|Expression|SelectExpression $select An array of expressions or one expression.
      * @param string|null $alias An alias. Actual if the first parameter is a string.
      */
     public function select($select, ?string $alias = null): self