diff --git a/SQL-Queries-on-Message-Queue.md b/SQL-Queries-on-Message-Queue.md
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+# SQL Queries on Message Queue
+
+SeaweedFS provides a powerful SQL query engine that allows you to query Message Queue topics using standard SQL syntax. This feature enables analytics, reporting, and data exploration on your message data using familiar SQL tools and PostgreSQL-compatible clients.
+
+## Overview
+
+The SQL query engine bridges the gap between SeaweedFS's Message Queue and traditional SQL databases by providing:
+
+- **PostgreSQL Wire Protocol Compatibility** - Use any PostgreSQL client, tool, or application
+- **Real-time + Historical Data** - Query both live messages and archived Parquet data
+- **Standard SQL Operations** - SELECT, aggregations, filtering, and schema operations
+- **Multiple Interface Options** - Database server mode and interactive CLI
+- **Secure Authentication** - MD5, password, and trust authentication methods
+
+## Architecture
+
+```
+┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
+│   SQL Clients   │    │  PostgreSQL     │    │  SeaweedFS      │
+│   (psql, apps)  │────│  Wire Protocol  │────│  SQL Engine     │
+└─────────────────┘    └─────────────────┘    └─────────────────┘
+                                                       │
+                                              ┌─────────────────┐
+                                              │ Hybrid Scanner  │
+                                              │ • Live Messages │
+                                              │ • Parquet Files │
+                                              └─────────────────┘
+```
+
+## Quick Start
+
+### 1. Start the Database Server
+
+```bash
+# Start PostgreSQL-compatible database server
+weed db -auth=md5 -users='{"admin":"secret","analyst":"readonly"}'
+
+# Or use a JSON file for credentials
+echo '{"admin":"secret","analyst":"readonly"}' > users.json
+weed db -auth=md5 -users="@users.json" -port=5432
+```
+
+### 2. Connect with psql
+
+```bash
+# Connect using psql
+PGPASSWORD=secret psql -h localhost -p 5432 -U admin -d default
+
+# Or with connection string
+psql "postgresql://admin:secret@localhost:5432/default"
+```
+
+### 3. Start Querying
+
+```sql
+-- List available databases (MQ namespaces)
+SHOW DATABASES;
+
+-- Switch to a namespace
+USE my_namespace;
+
+-- List tables (MQ topics) 
+SHOW TABLES;
+
+-- Query message data
+SELECT * FROM user_events WHERE _ts > '2025-01-01' LIMIT 10;
+
+-- Perform basic aggregations
+SELECT COUNT(*) as total_events FROM user_events;
+```
+
+## Commands and Interfaces
+
+### Database Server Mode (`weed db`)
+
+Starts a PostgreSQL-compatible database server that accepts connections from any PostgreSQL client.
+
+```bash
+# Basic usage
+weed db
+
+# Production setup with MD5 authentication
+weed db -auth=md5 -users="@/etc/seaweedfs/users.json" \
+        -host=0.0.0.0 -port=5432
+
+# With TLS encryption
+weed db -auth=md5 -users="@users.json" \
+        -tls-cert=/etc/ssl/server.crt \
+        -tls-key=/etc/ssl/server.key
+
+# Custom configuration
+weed db -auth=md5 -users='{"admin":"pass"}' \
+        -port=5433 \
+        -master=master1:9333 \
+        -max-connections=200 \
+        -idle-timeout=2h
+```
+
+**Options:**
+- `-auth`: Authentication method (`trust`, `password`, `md5`)
+- `-users`: User credentials (JSON format or file)
+- `-host`: Database server host (default: `localhost`)
+- `-port`: Database server port (default: `5432`)
+- `-master`: SeaweedFS master server address
+- `-database`: Default database name
+- `-max-connections`: Maximum concurrent connections
+- `-idle-timeout`: Connection idle timeout
+- `-tls-cert`, `-tls-key`: TLS certificate and key files
+
+### Interactive CLI Mode (`weed sql`)
+
+Provides an interactive SQL shell for quick queries and exploration.
+
+```bash
+# Start interactive SQL shell
+weed sql -master=localhost:9333
+
+# Connect to specific namespace
+weed sql -master=localhost:9333 -namespace=analytics
+
+# Execute single query
+weed sql -master=localhost:9333 -exec="SHOW TABLES"
+```
+
+## Authentication and Security
+
+### Authentication Methods
+
+1. **`trust`** (Default - Development Only)
+   - No authentication required
+   - Suitable for local development only
+
+2. **`md5`** (Recommended for Production)
+   - Secure MD5 hash + salt authentication
+   - Compatible with all PostgreSQL clients
+   - Safe even without TLS
+
+3. **`password`** (Development + TLS Only)
+   - Clear text password transmission
+   - Requires TLS encryption for production use
+
+### Credential Formats
+
+#### JSON Format (Inline)
+```bash
+weed db -auth=md5 -users='{"admin":"secret","analyst":"readonly"}'
+
+# Supports any special characters
+weed db -auth=md5 -users='{"admin":"pass;with;semicolons","user":"pass:with:colons"}'
+```
+
+#### File Format (Recommended)
+```bash
+# Create users file
+cat > /etc/seaweedfs/users.json << EOF
+{
+  "admin": "strong_password_123!",
+  "analyst": "readonly_user_456",
+  "developer": "dev_access_789"
+}
+EOF
+
+# Use file-based credentials
+weed db -auth=md5 -users="@/etc/seaweedfs/users.json"
+```
+
+### TLS Encryption
+
+```bash
+# Generate certificates (example)
+openssl req -x509 -newkey rsa:2048 -keyout server.key -out server.crt -days 365 -nodes
+
+# Start with TLS
+weed db -auth=md5 -users="@users.json" \
+        -tls-cert=server.crt -tls-key=server.key
+```
+
+## SQL Operations
+
+### Schema Operations
+
+```sql
+-- List all databases (MQ namespaces)
+SHOW DATABASES;
+
+-- Switch database context
+USE namespace_name;
+
+-- List tables in current database (MQ topics)
+SHOW TABLES;
+
+-- Describe table schema
+DESCRIBE table_name;
+SHOW COLUMNS FROM table_name;
+
+-- Note: CREATE TABLE, DROP TABLE and ALTER TABLE are not supported
+```
+
+### Data Queries
+
+```sql
+-- Basic SELECT
+SELECT * FROM user_events LIMIT 10;
+
+-- Filtering with WHERE clauses
+SELECT * FROM user_events 
+WHERE event_type = 'login' 
+  AND _ts > '2025-01-01';
+
+-- Basic aggregations (limited support)
+SELECT COUNT(*) FROM user_events;
+SELECT MIN(timestamp), MAX(timestamp) FROM user_events;
+SELECT SUM(value_column), AVG(value_column) FROM user_events;
+
+-- System columns (available on all topics)
+SELECT 
+    _ts,            -- Message timestamp (formatted, supports string parsing in WHERE)
+    _key,           -- Message key
+    _source,        -- Data source (parquet file or live)
+    *
+FROM user_events;
+```
+
+**Note:** The `_ts` system column supports automatic parsing of timestamp strings in WHERE clauses. Supported formats include `'2025-01-01'`, `'2025-01-01T15:30:00Z'`, `'2025-01-01 15:30:00'`, etc. Other timestamp columns require exact value matching.
+
+### Supported WHERE Clause Operations
+
+```sql
+-- Comparison operators
+SELECT * FROM user_events WHERE user_id = 123;
+SELECT * FROM user_events WHERE _ts > '2025-01-01';
+SELECT * FROM user_events WHERE value <= 100;
+
+-- Pattern matching
+SELECT * FROM user_events WHERE event_type LIKE 'login%';
+
+-- IN clause  
+SELECT * FROM user_events WHERE event_type IN ('login', 'logout', 'signup');
+
+-- Combining conditions
+SELECT * FROM user_events 
+WHERE event_type = 'purchase' 
+  AND _ts > '2025-01-01' 
+  AND value > 50;
+```
+
+### INTERVAL Expressions and Timestamp Arithmetic
+
+```sql
+-- Basic INTERVAL expressions
+SELECT INTERVAL '1 hour';
+SELECT INTERVAL '30 minutes';
+SELECT INTERVAL '24 hours';
+SELECT INTERVAL '7 days';
+
+-- Timestamp arithmetic with INTERVAL
+SELECT NOW() - INTERVAL '1 hour' as one_hour_ago;
+SELECT CURRENT_TIMESTAMP - INTERVAL '24 hours' as yesterday;
+
+-- Using INTERVAL in WHERE clauses for time-based filtering
+SELECT * FROM user_events 
+WHERE _ts >= NOW() - INTERVAL '1 hour';
+
+SELECT * FROM user_events 
+WHERE _ts >= CURRENT_TIMESTAMP - INTERVAL '24 hours'
+  AND _ts < CURRENT_TIMESTAMP - INTERVAL '1 hour';
+
+-- Supported INTERVAL units
+SELECT NOW() - INTERVAL '1 second';
+SELECT NOW() - INTERVAL '5 minutes';  
+SELECT NOW() - INTERVAL '2 hours';
+SELECT NOW() - INTERVAL '3 days';
+SELECT NOW() - INTERVAL '1 week';
+```
+
+### Limitations
+
+**Not Supported:**
+- `ORDER BY` clauses
+- `GROUP BY` clauses  
+- `HAVING` clauses
+- `JOIN` operations
+- `CREATE TABLE` statements
+- `DROP TABLE` statements
+- `ALTER TABLE` statements
+- Complex aggregations with grouping
+- Window functions
+- Subqueries
+
+## Client Examples
+
+### Python (psycopg2)
+
+```python
+import psycopg2
+import pandas as pd
+
+# Connect to SeaweedFS SQL server
+conn = psycopg2.connect(
+    host="localhost",
+    port=5432,
+    user="admin", 
+    password="secret",
+    database="default"
+)
+
+# Query data  
+query = """
+SELECT event_type, user_id, _ts
+FROM user_events 
+WHERE _ts > '2025-01-01'
+LIMIT 100
+"""
+
+# Use pandas for easy data analysis
+df = pd.read_sql(query, conn)
+print(df)
+
+# Close connection
+conn.close()
+```
+
+### Java JDBC
+
+```java
+import java.sql.*;
+
+public class SeaweedFSQuery {
+    public static void main(String[] args) throws SQLException {
+        String url = "jdbc:postgresql://localhost:5432/default";
+        Connection conn = DriverManager.getConnection(url, "admin", "secret");
+        
+        String query = "SELECT * FROM user_events LIMIT 10";
+        Statement stmt = conn.createStatement();
+        ResultSet rs = stmt.executeQuery(query);
+        
+        while (rs.next()) {
+            System.out.println("User ID: " + rs.getInt("user_id"));
+            System.out.println("Event: " + rs.getString("event_type"));
+            System.out.println("Timestamp: " + rs.getTimestamp("timestamp"));
+        }
+        
+        conn.close();
+    }
+}
+```
+
+### Go (lib/pq)
+
+```go
+package main
+
+import (
+    "database/sql"
+    "fmt"
+    "log"
+    _ "github.com/lib/pq"
+)
+
+func main() {
+    connStr := "host=localhost port=5432 user=admin password=secret dbname=default sslmode=disable"
+    db, err := sql.Open("postgres", connStr)
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer db.Close()
+    
+    query := "SELECT event_type, user_id, _ts FROM user_events WHERE _ts > '2025-01-01' LIMIT 100"
+    rows, err := db.Query(query)
+    if err != nil {
+        log.Fatal(err)
+    }
+    defer rows.Close()
+    
+    for rows.Next() {
+        var eventType string
+        var userID int
+        var timestamp string
+        if err := rows.Scan(&eventType, &userID, &timestamp); err != nil {
+            log.Fatal(err)
+        }
+        fmt.Printf("Event: %s, User: %d, Time: %s\n", eventType, userID, timestamp)
+    }
+}
+```
+
+### Node.js (pg)
+
+```javascript
+const { Client } = require('pg');
+
+const client = new Client({
+  host: 'localhost',
+  port: 5432,
+  user: 'admin',
+  password: 'secret',
+  database: 'default'
+});
+
+async function queryData() {
+  await client.connect();
+  
+  const query = `
+    SELECT event_type, user_id, timestamp
+    FROM user_events 
+    WHERE timestamp > $1
+    LIMIT 100
+  `;
+  
+  const result = await client.query(query, ['2024-01-01']);
+  
+  console.log('Recent Events:');
+  result.rows.forEach(row => {
+    console.log(`${row.event_type} by user ${row.user_id} at ${row.timestamp}`);
+  });
+  
+  await client.end();
+}
+
+queryData().catch(console.error);
+```
+
+## Data Sources and Architecture
+
+### Hybrid Message Scanner
+
+The SQL engine uses a hybrid approach to query both real-time and historical data:
+
+1. **Live Messages** - Queries unflushed messages directly from MQ brokers
+2. **Parquet Files** - Queries archived/flushed messages from Parquet storage
+3. **Seamless Integration** - Results are merged to provide complete data view
+
+### System Columns
+
+Every topic automatically includes system columns:
+
+- `_ts` - Message timestamp (formatted timestamp)
+- `_key` - Message partition key
+- `_source` - Data source identifier (parquet file path or "live")
+
+### Schema Evolution
+
+The SQL engine supports backward-compatible schema evolution:
+- New columns can be added to existing topics
+- Old queries continue to work with new data
+- Missing columns return NULL values
+
+## Performance Optimization
+
+### Fast Path Aggregations
+
+The engine optimizes common aggregation queries:
+
+```sql
+-- These queries use optimized fast paths
+SELECT COUNT(*) FROM user_events;
+SELECT MIN(timestamp) FROM user_events;  
+SELECT MAX(timestamp) FROM user_events;
+
+-- Add WHERE clauses for more specific queries
+SELECT COUNT(*) FROM user_events WHERE event_type = 'login';
+```
+
+### Query Best Practices
+
+1. **Use time-based filtering** for large datasets:
+   ```sql
+   SELECT * FROM events WHERE _ts >= '2025-01-01' AND _ts < '2025-02-01';
+   ```
+
+2. **Limit result sets** for exploration:
+   ```sql
+   SELECT * FROM events WHERE _ts > '2025-01-01' LIMIT 1000;
+   ```
+
+3. **Use appropriate indexes** on frequently queried columns (when supported)
+
+4. **Leverage system columns** for debugging:
+   ```sql
+   SELECT _source, _ts FROM events LIMIT 100;
+   ```
+
+## BI Tool Integration
+
+### Apache Superset
+
+```python
+# Database URI for Apache Superset
+postgresql://admin:secret@localhost:5432/default
+```
+
+### Grafana
+
+```yaml
+# Grafana datasource configuration
+apiVersion: 1
+datasources:
+  - name: SeaweedFS
+    type: postgres
+    url: localhost:5432
+    database: default
+    user: admin
+    password: secret
+    sslmode: disable
+```
+
+### Tableau
+
+Use the PostgreSQL connector with:
+- Server: `localhost`
+- Port: `5432`
+- Database: `default`
+- Username: `admin`
+- Password: `secret`
+
+## Troubleshooting
+
+### Common Issues
+
+1. **"Database server not running"**
+   ```bash
+   # Check if weed db is running
+   ps aux | grep "weed db"
+   
+   # Check port availability
+   netstat -ln | grep 5432
+   ```
+
+2. **"Authentication failed"**
+   ```bash
+   # Verify user credentials
+   cat users.json
+   
+   # Test with trust authentication
+   weed db -auth=trust
+   ```
+
+3. **"No data returned"**
+   ```sql
+   -- Check if topics exist
+   SHOW TABLES;
+   
+   -- Check data sources
+   SELECT _source FROM topic_name LIMIT 100;
+   
+   -- Check timestamp ranges
+   SELECT MIN(timestamp), MAX(timestamp) FROM topic_name;
+   ```
+
+4. **"Connection timeout"**
+   ```bash
+   # Increase timeout settings
+   weed db -idle-timeout=24h -max-connections=50
+   
+   # Check network connectivity
+   telnet localhost 5432
+   ```
+
+### Debug Mode
+
+Enable debug logging for troubleshooting:
+
+```bash
+# Set debug mode
+export GLOG_v=2
+
+# Start with verbose logging
+weed db -auth=md5 -users="@users.json" -v=2
+```
+
+### Performance Issues
+
+1. **Slow queries on large datasets**:
+   - Add time-based WHERE clauses
+   - Use LIMIT for exploration
+   - Consider data partitioning strategies
+
+2. **High memory usage**:
+   - Reduce concurrent connections
+   - Limit result set sizes
+   - Monitor broker memory usage
+
+3. **Network timeouts**:
+   - Increase idle timeout settings
+   - Check network stability between components
+   - Use connection pooling in applications
+
+## Production Deployment
+
+### Recommended Setup
+
+```bash
+# Production database server
+weed db \
+  -auth=md5 \
+  -users="@/etc/seaweedfs/users.json" \
+  -host=0.0.0.0 \
+  -port=5432 \
+  -master=master1:9333,master2:9333,master3:9333 \
+  -max-connections=100 \
+  -idle-timeout=1h \
+  -tls-cert=/etc/ssl/seaweedfs-db.crt \
+  -tls-key=/etc/ssl/seaweedfs-db.key
+```
+
+### High Availability
+
+- Run multiple `weed db` instances behind a load balancer
+- Use master server failover configuration
+- Monitor connection health and query performance
+- Implement connection pooling in client applications
+
+### Security Checklist
+
+- [ ] Use MD5 or password authentication (never trust in production)
+- [ ] Enable TLS encryption for data in transit
+- [ ] Store credentials in secure files with proper permissions
+- [ ] Limit database server network access with firewalls
+- [ ] Monitor authentication attempts and query patterns
+- [ ] Regular security updates and credential rotation
+
+## Related Documentation
+
+- [Seaweed Message Queue](Seaweed-Message-Queue.md)
+- [Security Configuration](Security-Configuration.md)
+- [Production Setup](Production-Setup.md)
+- [System Metrics](System-Metrics.md)
diff --git a/SQL-Quick-Reference.md b/SQL-Quick-Reference.md
new file mode 100644
index 0000000..12b2f62
--- /dev/null
+++ b/SQL-Quick-Reference.md
@@ -0,0 +1,195 @@
+# SQL Quick Reference
+
+Quick reference guide for SeaweedFS SQL queries on Message Queue topics.
+
+## Commands
+
+### Start Database Server
+```bash
+# Basic (development)
+weed db
+
+# Production with MD5 auth
+weed db -auth=md5 -users='{"admin":"secret"}' -host=0.0.0.0
+
+# With TLS encryption
+weed db -auth=md5 -users="@users.json" -tls-cert=server.crt -tls-key=server.key
+```
+
+### Interactive CLI
+```bash
+# Start SQL shell
+weed sql
+
+# Execute single query
+weed sql -exec="SHOW TABLES"
+```
+
+## Authentication
+
+### Credential Formats
+```bash
+# JSON inline
+-users='{"user1":"pass1","user2":"pass2"}'
+
+# JSON file
+-users="@/path/to/users.json"
+```
+
+### Auth Methods
+- `trust` - No auth (dev only)
+- `md5` - Hash + salt (recommended)
+- `password` - Clear text (TLS required)
+
+## Client Connections
+
+### psql
+```bash
+# Basic connection
+psql -h localhost -p 5432 -U admin -d default
+
+# With password
+PGPASSWORD=secret psql -h localhost -p 5432 -U admin -d default
+
+# Connection string
+psql "postgresql://admin:secret@localhost:5432/default"
+```
+
+### Programming Languages
+```python
+# Python
+import psycopg2
+conn = psycopg2.connect(host="localhost", port=5432, user="admin", password="secret", database="default")
+```
+
+```java
+// Java
+String url = "jdbc:postgresql://localhost:5432/default";
+Connection conn = DriverManager.getConnection(url, "admin", "secret");
+```
+
+```go
+// Go
+db, err := sql.Open("postgres", "host=localhost port=5432 user=admin password=secret dbname=default sslmode=disable")
+```
+
+## SQL Operations
+
+### Schema Commands
+```sql
+SHOW DATABASES;                    -- List MQ namespaces
+USE namespace_name;                -- Switch database  
+SHOW TABLES;                       -- List MQ topics
+DESCRIBE table_name;               -- Show table schema
+-- Note: CREATE TABLE, DROP TABLE and ALTER TABLE not supported
+```
+
+### Query Commands
+```sql
+-- Basic queries
+SELECT * FROM events LIMIT 10;
+SELECT * FROM events WHERE _ts > '2025-01-01';
+SELECT * FROM events WHERE status IN ('active', 'completed');
+SELECT COUNT(*) FROM events;
+
+-- System columns (available on all tables)
+SELECT _ts, _key, _source, * FROM events;
+
+-- Aggregations (optimized)
+SELECT COUNT(*) FROM events;
+SELECT MIN(timestamp), MAX(timestamp) FROM events;
+```
+
+### Time-based Queries
+```sql
+-- Time filtering with system timestamp column (_ts)
+-- Automatic string-to-timestamp conversion for _ts system column
+SELECT * FROM events 
+WHERE _ts >= '2025-01-01' 
+  AND _ts < '2025-02-01' 
+LIMIT 1000;
+
+-- INTERVAL expressions and timestamp arithmetic
+SELECT NOW() - INTERVAL '1 hour';
+SELECT * FROM events WHERE _ts >= NOW() - INTERVAL '24 hours';
+SELECT * FROM events WHERE _ts >= CURRENT_TIMESTAMP - INTERVAL '1 day';
+
+-- BETWEEN clauses with INTERVAL arithmetic
+SELECT * FROM events WHERE _ts BETWEEN NOW() - INTERVAL '1 week' AND NOW();
+SELECT * FROM events WHERE _ts BETWEEN '2025-01-01' AND '2025-12-31';
+
+-- Current time functions
+SELECT NOW(), CURRENT_TIMESTAMP, CURRENT_DATE FROM events LIMIT 1;
+```
+
+## System Columns
+
+Every topic includes these system columns:
+- `_ts` - Message timestamp (formatted timestamp, supports automatic string-to-timestamp conversion in WHERE clauses)
+- `_key` - Message partition key  
+- `_source` - Data source ("live" or parquet file path)
+
+**Note:** The `_ts` column supports automatic parsing of timestamp strings in WHERE clauses. Formats supported: `'2025-01-01'`, `'2025-01-01T15:30:00Z'`, `'2025-01-01 15:30:00'`, etc.
+
+## Troubleshooting
+
+### Check Status
+```sql
+-- Verify tables exist
+SHOW TABLES;
+
+-- Check data sources  
+SELECT _source FROM table_name LIMIT 100;
+
+-- Verify time range
+SELECT MIN(timestamp), MAX(timestamp) FROM table_name;
+```
+
+### Common Issues
+1. **No data**: Check `SHOW TABLES` and topic names
+2. **Auth failed**: Verify credentials in users file
+3. **Timeouts**: Increase `-idle-timeout` setting
+4. **Slow queries**: Add WHERE clauses and LIMIT
+
+### Debug Mode
+```bash
+# Enable verbose logging
+export GLOG_v=2
+weed db -v=2 ...
+```
+
+## Performance Tips
+
+1. **Filter by time** for large datasets:
+   ```sql
+   WHERE _ts >= '2025-01-01' AND _ts < '2025-02-01'
+   ```
+
+2. **Use LIMIT** for exploration:
+   ```sql
+   SELECT * FROM events WHERE _ts > '2025-01-01' LIMIT 1000
+   ```
+
+3. **Fast aggregations** (basic functions only):
+   ```sql
+   SELECT COUNT(*) FROM events;  -- Optimized
+   SELECT MIN(timestamp), MAX(timestamp) FROM events;  -- Optimized  
+   ```
+
+4. **Check data sources**:
+   ```sql
+   SELECT _source, _ts FROM events LIMIT 100;
+   ```
+
+## Limitations
+
+**Not Supported:**
+- `ORDER BY`, `GROUP BY`, `HAVING` clauses
+- `JOIN` operations between tables
+- `CREATE TABLE`, `DROP TABLE`, `ALTER TABLE` statements
+- Window functions and subqueries  
+- Complex aggregations with grouping
+
+## Links
+
+For detailed documentation, see [[SQL Queries on Message Queue]].
diff --git a/_Sidebar.md b/_Sidebar.md
index 5aa94e3..609f078 100644
--- a/_Sidebar.md
+++ b/_Sidebar.md
@@ -115,6 +115,8 @@
 
 ### Messaging
 * [[Seaweed Message Queue]]
+* [[SQL Queries on Message Queue]]
+* [[SQL Quick Reference]]
 
 ### Use Cases
 * [[Use Cases]]