Phrase searching means searching a database for words in a precise order. Different databases interpret searches differently. Some very few databases assume that two words next to each other should be searched as a phrase automatically. Most of the databases will put a boolean operator AND between two words.
In general, the easiest way to search for terms next to each other is to enclose them in quotation marks: “global warming”, “drunk driving”.
See the example in the database Web of Science below: the first search working mothers WITHOUT quotation marks gives 26 135 results:
The second search “working mothers” WITH quotation marks gives 1 288 results:
You may watch the same example in a short video (1:14) by Cannon Library (the link in the picture takes you to Youtube):