How many results?
While there are no standard rules for how many sources are considered to be adequate to complete a research topic, many indexes, such as Google limit Val's results to roughly 1000 sources, even though many thousands more results are listed. Most databases through Valencia do not impose a limit on your results. A search for tattoos in the Academic Search Complete database will return about 2400 articles. Do the same search in Google and over 46 million results are returned! However, Val will actually have access to fewer than a 1000 of those results. For some people, a thousand results might be a perfect pool to begin with, while for others they might prefer to narrow to a hundred articles or less.
The bottom line: In many instances, the research databases give you not only more credible resources, but a larger pool that is accessible.