input: Write a python function to create a web service for a database that accepts requests from a client, queries the database, and returns the results back to the client.
  assert create_web_service(request1)==expected_response1
  assert create_web_service(request2)==expected_response2
  assert create_web_service(request3)==expected_response3
output: from flask import Flask, request, jsonify
  import sqlite3
  
  app = Flask(__name__)
  
  def create_web_service(db_path):
      @app.route('/query', methods=['POST'])
      def query_db():
          query = request.json['query']
          conn = sqlite3.connect(db_path)
          cursor = conn.cursor()
          cursor.execute(query)
          results = cursor.fetchall()
          conn.close()
          return jsonify(results)
  
      return app
  
  # Example usage:
  # app = create_web_service('example.db')
  # app.run()