storing actors in a movie class

I am writing a program that reads from a file called movies.db that has a list of movies and each movie is a record containing information about each movie. It reads the records into a vector. The problem I have is how do I make it so that it can store any number of actors in each record? eg, one movie may have one actor, while another may have five. The program than allows movies to be searched by actor. How do I make it so that a record can have any number of actors stored in it plus the movie title, director, running time, etc. etc.