This Python script converts the schema of an SQLite database to DBML format. It exports the table definitions and foreign key relationships, allowing for easy visualization of the database structure using tools like dbdiagram.io.

sqlite_schema_to_dbml.py

"""
Copyright (C) 2024 promto-c

Permission Notice:
- You are free to use, copy, modify, and distribute this software for any purpose.
- No restrictions are imposed on the use of this software.
- You do not need to give credit or include this notice in your work.
- Use at your own risk.
- This software is provided "AS IS" without any warranty, either expressed or implied.
"""
# Type Checking Imports
# ---------------------
from typing import List, Tuple

# Standard Library Imports
# ------------------------
import sqlite3


def export_schema(db_path: str, output_file: str) -> None:
    """Exports the schema of the given SQLite database to a SQL file.

    Args:
        db_path: The path to the SQLite database file.
        output_file: The path to the output file where the schema will be saved.
    """
    conn = sqlite3.connect(db_path)
    cursor = conn.cursor()
    
    with open(output_file, 'w') as f:
        for line in conn.iterdump():
            f.write(f'{line}\n')
    
    conn.close()

def convert_to_dbml(db_path: str, dbml_output: str) -> None:
    """Converts the schema of the given SQLite database to DBML format and saves it to a file.

    Args:
        db_path: The path to the SQLite database file.
        dbml_output: The path to the output file where the DBML will be saved.
    """
    conn = sqlite3.connect(db_path)
    cursor = conn.cursor()
    
    # Get all user-defined tables, excluding SQLite internal tables
    tables: List[Tuple[str]] = cursor.execute(
        "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%';"
    ).fetchall()
    dbml_lines: List[str] = []

    for table in tables:
        table_name: str = table[0]
        dbml_lines.append(f"Table {table_name} {{")
        columns: List[Tuple[int, str, str, int, str, int]] = cursor.execute(f"PRAGMA table_info({table_name});").fetchall()
        
        for column in columns:
            col_name: str = column[1]
            col_type: str = column[2]
            col_pk: str = "pk" if column[5] else ""
            col_def: str = f"{col_name} {col_type} {col_pk}".strip()
            dbml_lines.append(f"  {col_def}")
        
        dbml_lines.append("}")
    
    # Add relationships
    for table in tables:
        table_name: str = table[0]
        foreign_keys: List[Tuple[int, int, str, str, str, str, str, str, str, str]] = cursor.execute(f"PRAGMA foreign_key_list({table_name});").fetchall()
        
        for fk in foreign_keys:
            fk_table: str = fk[2]
            fk_from: str = fk[3]
            fk_to: str = fk[4]
            dbml_lines.append(f"Ref: {table_name}.{fk_from} > {fk_table}.{fk_to}")

    conn.close()
    
    with open(dbml_output, 'w') as f:
        f.write('\n'.join(dbml_lines))

if __name__ == '__main__':
    # Export SQLite schema
    # export_schema('your_database.db', 'schema.sql')

    # Convert to DBML
    convert_to_dbml('your_database.db', 'output.dbml')