Update index.md

Author: BohuTANG

docs/en/sql-reference/20-sql-functions/index.md

@@ -2,68 +2,73 @@
 title: SQL Function Reference
 ---
 
-This page provides a reference for all SQL functions available in Databend, organized by category.
+Databend provides comprehensive SQL functions for all types of data processing. Functions are organized by importance and usage frequency.
 
-## Core SQL Functions
+## Core Data Functions
 
 | Category | Description |
 |----------|-------------|
-| [Numeric Functions](./04-numeric-functions/index.md) | Mathematical operations for numerical data processing and analysis |
-| [String Functions](./06-string-functions/index.md) | Text manipulation and pattern matching operations for data processing |
-| [Date & Time Functions](./05-datetime-functions/index.md) | Date and time manipulation for temporal data analysis |
-| [Aggregate Functions](./07-aggregate-functions/index.md) | Functions that perform calculations across multiple rows |
-| [Window Functions](./08-window-functions/index.md) | Functions that operate on a set of rows related to the current row |
+| [Numeric Functions](./04-numeric-functions/index.md) | Mathematical operations and calculations |
+| [String Functions](./06-string-functions/index.md) | Text manipulation and string processing |
+| [Date & Time Functions](./05-datetime-functions/index.md) | Date, time, and temporal operations |
+| [Interval Functions](./05-interval-functions/index.md) | Time unit conversion and interval creation |
+| [Conversion Functions](./02-conversion-functions/index.md) | Type casting and data format conversions |
+| [Conditional Functions](./03-conditional-functions/index.md) | Logic and control flow operations |
 
-## Data Type Functions
+## Analytics Functions
 
 | Category | Description |
 |----------|-------------|
-| [Conversion Functions](./02-conversion-functions/index.md) | Type conversion and casting operations between different data types |
-| [Structured & Semi-Structured Functions](./10-semi-structured-functions/index.md) | Functions for processing JSON, arrays, objects, maps, and other structured data types |
+| [Aggregate Functions](./07-aggregate-functions/index.md) | Statistical calculations across multiple rows |
+| [Window Functions](./08-window-functions/index.md) | Advanced analytics with window operations |
+| [Bitmap Functions](./01-bitmap-functions/index.md) | High-performance bitmap operations and analytics |
 
-## Logical and Control Functions
+## Semi-Structured Data
 
 | Category | Description |
 |----------|-------------|
-| [Conditional Functions](./03-conditional-functions/index.md) | Logic-based data transformation and flow control functions |
-| [Interval Functions](./05-interval-functions/index.md) | Creation and manipulation of time intervals for date calculations |
+| [Semi-Structured Functions](./10-semi-structured-functions/index.md) | JSON, arrays, objects, and nested data processing |
 
-## System and Metadata Functions
+## AI & Search
 
 | Category | Description |
 |----------|-------------|
-| [Table Functions](./17-table-functions/index.md) | Functions that return result sets as tables |
-| [System Functions](./16-system-functions/index.md) | Functions for accessing system information and management |
-| [Context Functions](./15-context-functions/index.md) | Functions for accessing session and environment information |
+| [AI Functions](./11-ai-functions/index.md) | Natural language processing and AI capabilities |
+| [Vector Functions](./11-vector-functions/index.md) | Vector similarity and distance calculations |
+| [Search Functions](./10-search-functions/index.md) | Full-text search and relevance scoring |
 
-## Specialized Analytics Functions
+## Data Management
 
 | Category | Description |
 |----------|-------------|
-| [Geo Functions](./09-geo-functions/index.md) | Geographic coordinate and H3 geospatial operations |
-| [Geometry Functions](./09-geometry-functions/index.md) | Geometric shape operations and spatial calculations |
-| [Search Functions](./10-search-functions/index.md) | Full-text search capabilities and text relevance |
+| [Table Functions](./17-table-functions/index.md) | File inspection, data generation, and system information |
+| [Dictionary Functions](./19-dictionary-functions/index.md) | Real-time external data source queries (MySQL, Redis) |
+| [Sequence Functions](./18-sequence-functions/index.md) | Auto-incrementing sequence value generation |
 
-## AI and Vector Functions
+## Spatial Functions
 
 | Category | Description |
 |----------|-------------|
-| [AI Functions](./11-ai-functions/index.md) | Natural language processing and AI capabilities |
-| [Vector Functions](./11-vector-functions/index.md) | Vector similarity and distance calculations |
+| [Geo Functions](./09-geo-functions/index.md) | Geographic coordinates and H3 geospatial operations |
+| [Geometry Functions](./09-geometry-functions/index.md) | Geometric shapes and spatial calculations |
+
+## Security & Integrity
+
+| Category | Description |
+|----------|-------------|
+| [Hash Functions](./12-hash-functions/index.md) | Data hashing and integrity verification |
+| [UUID Functions](./13-uuid-functions/index.md) | Universally unique identifier generation |
+| [IP Address Functions](./14-ip-address-functions/index.md) | Network address manipulation and validation |
 
-## Data Integrity Functions
+## System Functions
 
 | Category | Description |
 |----------|-------------|
-| [Hash Functions](./12-hash-functions/index.md) | Data hashing and fingerprinting algorithms |
-| [UUID Functions](./13-uuid-functions/index.md) | Universally unique identifier generation and handling |
-| [IP Address Functions](./14-ip-address-functions/index.md) | IP address manipulation and conversion |
-| [Bitmap Functions](./01-bitmap-functions/index.md) | Bit-level operations and manipulations |
+| [System Functions](./16-system-functions/index.md) | System information and management operations |
+| [Context Functions](./15-context-functions/index.md) | Current session, user, and database information |
 
-## Utility Functions
+## Development Tools
 
 | Category | Description |
 |----------|-------------|
-| [Sequence Functions](./18-sequence-functions/index.md) | Sequence generation and manipulation |
-| [Dictionary Functions](./19-dictionary-functions/index.md) | External data source integration |
-| [Test Functions](./19-test-functions/index.md) | Functions for testing and development purposes |
+| [Test Functions](./19-test-functions/index.md) | Testing and debugging utilities |