Did you know that when you enter an entire sentence into Google it searches each.. word.. individually? That's why you get millions of results back! Luckily Google does a decent job of returning relevant results from a sentence. Unlike Google, databases can't understand an entire sentence. You will need to break your topic down into the most important ideas, or keywords. Even Google will give you better results if you use relevant keywords!
Let's try with an example topic: How does playing video games as a child affect reading comprehension?
Keywords: video games, child, reading comprehension