input: Write a function to create and execute queries on three different databases (MySQL, MongoDB, PostgreSQL) and then render the results on a web page using the respective database libraries. The function should connect to each database, define a query, execute it, fetch the results, close the connections, and finally render the data on the web page.
  
  
  def query_databases():
      import pymysql
      from pymongo import MongoClient
      import psycopg2
  
      # connect to MySQL
      connection_mysql = pymysql.connect(host='localhost', user='root', password='password', database='db_name')
  
      # connect to MongoDB
      client = MongoClient('mongodb://localhost:27017')
  
      # connect to PostgreSQL
      connection_postgresql = psycopg2.connect(host='localhost', user='postgres', password='password', dbname='db_name')
  
      # define a query for each database
      query_mysql = 'SELECT * FROM table_name'
      query_mongodb = {'name': 'John Doe'}
      query_postgresql = 'SELECT * FROM table_name WHERE age > 18'
  
      # execute the query and fetch the results
      cursor_mysql = connection_mysql.cursor()
      cursor_mysql.execute(query_mysql)
      result_mysql = cursor_mysql.fetchall()
  
      result_mongodb = client.db_name.collection_name.find(query_mongodb)
  
      cursor_postgresql = connection_postgresql.cursor()
      cursor_postgresql.execute(query_postgresql)
      result_postgresql = cursor_postgresql.fetchall()
  
      # close the connections
      cursor_mysql.close()
      connection_mysql.close()
      client.close()
      cursor_postgresql.close()
      connection_postgresql.close()
  
      # return the results
      return {
          'data_mysql': result_mysql,
          'data_mongodb': list(result_mongodb),
          'data_postgresql': result_postgresql
      }
  
  assert query_databases() == {
      'data_mysql': [('John', 'Doe', 25), ('Jane', 'Doe', 23)],
      'data_mongodb': [{'name': 'John Doe', 'age': 25}, {'name': 'Jane Doe', 'age': 23}],
      'data_postgresql': [('John', 'Doe', 25), ('Jane', 'Doe', 23)]
  }
  
output: def query_databases():
      import pymysql
      from pymongo import MongoClient
      import psycopg2
  
      connection_mysql = pymysql.connect(host='localhost', user='root', password='password', database='db_name')
      client = MongoClient('mongodb://localhost:27017')
      connection_postgresql = psycopg2.connect(host='localhost', user='postgres', password='password', dbname='db_name')
  
      query_mysql = 'SELECT * FROM table_name'
      query_mongodb = {'name': 'John Doe'}
      query_postgresql = 'SELECT * FROM table_name WHERE age > 18'
  
      cursor_mysql = connection_mysql.cursor()
      cursor_mysql.execute(query_mysql)
      result_mysql = cursor_mysql.fetchall()
  
      result_mongodb = client.db_name.collection_name.find(query_mongodb)
  
      cursor_postgresql = connection_postgresql.cursor()
      cursor_postgresql.execute(query_postgresql)
      result_postgresql = cursor_postgresql.fetchall()
  
      cursor_mysql.close()
      connection_mysql.close()
      client.close()
      cursor_postgresql.close()
      connection_postgresql.close()
  
      return {
          'data_mysql': result_mysql,
          'data_mongodb': list(result_mongodb),
          'data_postgresql': result_postgresql
      }