update index pages as part of docs improvement to make breadcrumbs clickable

docs/en/engines/engine-reference-links.json

@@ -0,0 +1,12 @@
+[
+	{
+		"title": "Database Engines",
+		"description": "Database engines determine how ClickHouse interacts with tables and manages data storage.",
+		"url": "/docs/en/sql-reference/syntax/"
+	},
+	{
+		"title": "Table Engines",
+		"description": "Table engines determine how data is stored, accessed, and manipulated within tables.",
+		"url": "/docs/en/sql-reference/formats/"
+	}
+]

docs/en/engines/index.md

@@ -0,0 +1,16 @@
+---
+slug: /en/engines/
+---
+
+import { TwoColumnList } from '/src/components/two_column_list'
+import { ClickableSquare } from '/src/components/clickable_square'
+import { HorizontalDivide } from '/src/components/horizontal_divide'
+import { ViewAllLink } from '/src/components/view_all_link'
+import { VideoContainer } from '/src/components/video_container'
+import LinksDeployment from './engine-reference-links.json'
+
+# Engines
+
+<HorizontalDivide />
+
+<TwoColumnList items={LinksDeployment} />

docs/en/sql-reference/aggregate-functions/index.md

@@ -1,7 +1,10 @@
 ---
-slug: /en/sql-reference/aggregate-functions/
+slug: /en/sql-reference/functions/aggregate-functions/
-sidebar_label: Aggregate Functions
 sidebar_position: 33
+displayed_sidebar: sqlreference
+toc_folder_title: Aggregate Functions
+toc_priority: 27
+toc_title: Aggregate Functions
 ---
 
 # Aggregate Functions

docs/en/sql-reference/aggregate-functions/reference/index.md

@@ -1,8 +1,10 @@
 ---
 slug: /en/sql-reference/aggregate-functions/reference/
-toc_folder_title: Reference
 sidebar_position: 36
-toc_hidden: true
+toc_folder_title: Reference
+toc_priority: 1
+toc_title: List of Aggregate Functions
+displayed_sidebar: sqlreference
 ---
 
 # List of Aggregate Functions

docs/en/sql-reference/functions/functions-index.md

@@ -0,0 +1,19 @@
+---
+slug: /en/sql-reference/functions/
+sidebar_position: 1
+sidebar_label: Overview
+displayed_sidebar: sqlreference
+---
+
+import { TwoColumnList } from '/src/components/two_column_list'
+import { ClickableSquare } from '/src/components/clickable_square'
+import { HorizontalDivide } from '/src/components/horizontal_divide'
+import { ViewAllLink } from '/src/components/view_all_link'
+import { VideoContainer } from '/src/components/video_container'
+import LinksDeployment from './functions-reference-links.json'
+
+# Functions
+
+ClickHouse offers a wide array of functions that help you perform various operations on your data, and are broadly categorized into four kinds:
+
+<TwoColumnList items={LinksDeployment} />

docs/en/sql-reference/functions/functions-reference-links.json

@@ -0,0 +1,22 @@
+[
+	{
+		"title": "Regular Functions",
+		"description": "Functions which perform operations on individual rows of data. They can manipulate strings, numbers, and dates, among other things.",
+		"url": "/docs/en/sql-reference/functions/regular-functions/"
+	},
+	{
+		"title": "Aggregate Functions",
+		"description": "Functions which operate on data across multiple rows, returning a single result. They are typically used with the GROUP BY clause.",
+		"url": "/docs/en/sql-reference/functions/regular-functions/"
+	},
+	{
+		"title": "Table Functions",
+		"description": "Functions which enable complex data selection and transformation, often involving external data sources or special table structures.",
+		"url": "/docs/en/sql-reference/functions/table-functions/"
+	},
+	{
+		"title": "Window Functions",
+		"description": "Functions which perform calculations across a set of table rows that are related to the current row. They are useful for running totals, moving averages, and other analytics.",
+		"url": "/docs/en/sql-reference/functions/window-functions/"
+	}
+]

docs/en/sql-reference/functions/index.md

@@ -1,7 +1,8 @@
 ---
-slug: /en/sql-reference/functions/
+slug: /en/sql-reference/functions/regular-functions/
 sidebar_position: 1
 sidebar_label: Overview
+displayed_sidebar: sqlreference
 ---
 
 # Regular Functions

docs/en/sql-reference/index.md

@@ -13,9 +13,11 @@ import LinksDeployment from './sql-reference-links.json'
 
 # ClickHouse SQL Reference
 
-ClickHouse supports a declarative query language based on SQL that is identical to the ANSI SQL standard in many cases.
+ClickHouse supports a familiar declarative query language based on SQL that is identical to the ANSI SQL standard in many cases, but offers a host of additional functionality.
 
-Supported queries include GROUP BY, ORDER BY, subqueries in FROM, JOIN clause, IN operator, window functions and scalar subqueries.
+The SQL reference page serves as a comprehensive guide to help users understand and make use of ClickHouse's query language and functionality. It contains information about the supported syntax,
+data types, statements and wide range of input and output formats supported in ClickHouse as well as information on database and table engines and a large number of functions that
+make ClickHouse such an efficient and versatile tool.
 
 <HorizontalDivide />
 

docs/en/sql-reference/sql-reference-links.json

@@ -1,12 +1,32 @@
 [
+	{
+		"title": "Syntax",
+		"description": "A quick reference for the supported syntax in ClickHouse.",
+		"url": "/docs/en/sql-reference/syntax/"
+	},
+	{
+		"title": "Input and Output Formats",
+		"description": "A list of available Input and Output formats for handling your data.",
+		"url": "/docs/en/sql-reference/formats/"
+	},
 	{
 		"title": "Statements",
-		"description": "A list of available SQL statements in ClickHouse",
+		"description": "A list of available SQL statements in ClickHouse.",
 		"url": "/docs/en/sql-reference/statements/"
 	},
 	{
 	"title": "Database and Table Engines",
-	"description": "Engines determine where and how your data is stored",
+	"description": "Information on database and table engines which determine where and how your data is stored.",
-	"url": "/docs/en/engines/table-engines"
+	"url": "/docs/en/engines/engines"
+	},
+	{
+		"title": "Functions",
+		"description": "A complete and ever expanding list of functions for manipulating and transforming your data.",
+		"url": "/docs/en/engines/engines"
+	},
+	{
+		"title": "Other Features",
+		"description": "Additional features which are unique to ClickHouse.",
+		"url": "/docs/en/engines/engines"
 	}
 ]