I searched Google a lot over this topic but was not satisfied with answers I got, I am having a website and I want that users from that website should be able to log into wordpress as well, For this purpose having one database would be a better idea or having two seperate database is a good idea, my original database is going more than 52 MB , with 2000 users, But I fear if I make separate database I wouldn't be able to integrate website with blog in future,
2 databases gives you a bit more security but one is way simpler However, even if your two website systems are held in one database you will still have integration issues with wordpress. Your current database is still small, don't worry about the size of it.