input: Write a python function to query a database and retrieve specified columns from a given table.
  assert query_database('users', 'name, age')==[('Alice', 30), ('Bob', 25)]
  assert query_database('products', 'id, name')==[(1, 'Laptop'), (2, 'Phone')]
  assert query_database('orders', 'order_id, product_id')==[(101, 1), (102, 2)]
output: def query_database(table, columns):
      import sqlite3
      # Create an in-memory SQLite database
      conn = sqlite3.connect(':memory:')
      cursor = conn.cursor()
  
      # Create sample tables and insert data
      cursor.execute('CREATE TABLE users (name TEXT, age INTEGER)')
      cursor.execute("INSERT INTO users (name, age) VALUES ('Alice', 30)")
      cursor.execute("INSERT INTO users (name, age) VALUES ('Bob', 25)")
  
      cursor.execute('CREATE TABLE products (id INTEGER, name TEXT)')
      cursor.execute("INSERT INTO products (id, name) VALUES (1, 'Laptop')")
      cursor.execute("INSERT INTO products (id, name) VALUES (2, 'Phone')")
  
      cursor.execute('CREATE TABLE orders (order_id INTEGER, product_id INTEGER)')
      cursor.execute("INSERT INTO orders (order_id, product_id) VALUES (101, 1)")
      cursor.execute("INSERT INTO orders (order_id, product_id) VALUES (102, 2)")
  
      # Query the specified columns from the given table
      cursor.execute(f'SELECT {columns} FROM {table}')
      results = cursor.fetchall()
  
      # Close the connection
      conn.close()
  
      return results