database-scout

Read-only exploration tool for SQLite / PostgreSQL databases — inspect table schemas, preview data, generate ER diagrams, and run safe queries.

Feature Overview

Feature	Description
List all tables	Show tables and views in the database, with row counts
Inspect table schema	Column names, types, constraints (PK/FK/NOT NULL), indexes, defaults
Data preview	View the first N rows of a table
ER diagram generation	Output Mermaid erDiagram syntax, ready to render
Safe read-only queries	Only SELECT/WITH/EXPLAIN allowed; write operations are blocked

Security Mechanisms

• Connection-level read-only: SQLite opens with ?mode=ro URI; PostgreSQL uses SET SESSION READ ONLY
• SQL whitelist: Only statements starting with SELECT / WITH / EXPLAIN / PRAGMA / SHOW are allowed
• Dangerous keyword blocking: INSERT, UPDATE, DELETE, DROP, ALTER, CREATE, and 30+ other keywords are blocked
• Multi-statement blocking: Semicolon-separated multiple SQL statements are rejected (prevents injection)
• Identifier escaping: Table names are double-quote escaped to prevent SQL injection

Quick Start

# List all tables in a SQLite database
python3 scripts/db_explorer.py --db-path data.db list-tables

# Inspect table schema
python3 scripts/db_explorer.py --db-path data.db describe users

# Preview data (default 20 rows)
python3 scripts/db_explorer.py --db-path data.db preview orders --limit 10

# Generate Mermaid ER diagram
python3 scripts/db_explorer.py --db-path data.db er-diagram

# Run a read-only query
python3 scripts/db_explorer.py --db-path data.db query "SELECT name, age FROM users WHERE age > 18 LIMIT 10"

PostgreSQL

# Connect to PostgreSQL
python3 scripts/db_explorer.py --db-type postgres --dsn "host=localhost dbname=mydb user=reader" list-tables

# Inspect table schema
python3 scripts/db_explorer.py --db-type postgres --dsn "host=localhost dbname=mydb user=reader" describe orders

Detailed Usage

Parameters

Parameter	Required	Default	Description
--db-type	No	sqlite	Database type: sqlite or postgres
--db-path	Yes (for SQLite)	—	Path to the SQLite database file
--dsn	Yes (for PostgreSQL)	—	PostgreSQL connection string

Subcommands

Command	Description	Example
list-tables	List all tables/views	list-tables
describe <table>	Show detailed table schema	describe users
preview <table> [--limit N / -n N]	Preview the first N rows	preview orders --limit 5
er-diagram	Generate Mermaid ER diagram	er-diagram
query "<sql>"	Run a read-only SQL query	query "SELECT count(*) FROM users"

Output Examples

list-tables

[
  {"name": "users", "type": "table", "row_count": 1500},
  {"name": "orders", "type": "table", "row_count": 8200},
  {"name": "user_stats", "type": "view", "row_count": 1500}
]

describe

{
  "table": "orders",
  "row_count": 8200,
  "columns": [
    {"cid": 0, "name": "id", "type": "INTEGER", "notnull": true, "default": null, "primary_key": true},
    {"cid": 1, "name": "user_id", "type": "INTEGER", "notnull": true, "default": null, "primary_key": false},
    {"cid": 2, "name": "amount", "type": "REAL", "notnull": false, "default": "0.0", "primary_key": false}
  ],
  "foreign_keys": [
    {"from": "user_id", "to_table": "users", "to_column": "id"}
  ],
  "indexes": [
    {"name": "idx_orders_user_id", "unique": false, "columns": ["user_id"]}
  ]
}

er-diagram (Mermaid)

erDiagram
    users {
        INTEGER id PK
        TEXT name
        TEXT email
        INTEGER age
    }
    orders {
        INTEGER id PK
        INTEGER user_id FK
        REAL amount
        TEXT created_at
    }
    users ||--o{ orders : "user_id"

Dependencies

• Python 3.8+ (sqlite3 is a built-in module)
• PostgreSQL support requires: pip install psycopg2-binary