Instead of a one-time, linear search strategy, uncovering relevant sources involves cycles of exploration and refinement.
Building a database search strategy begins with one's understanding of a topic using keywords as search terms. Your search is then refined by using more relevant search terms contained in the search results.
No one library database contains all the articles written on a topic (sorry to say), so it is important to search in multiple library databases to understand how different disciplines are researching a topic.
It's no mistake that the key to conducting a successful review of the literature is found within the word, "Research": Re-search for sources by trying a variety of search terms and exploring different fields of study using subject databases.