 In this video, we'll be looking at Boolean operators, the small but very important words that are used to connect keywords in a database search. In another video, we talked about identifying keywords by pulling core concepts out of a research topic and listing synonymous and like terms for each of those concepts as shown in this table. But how do we enter these terms in a database? It's not effective to simply type all of the keywords into the search box as the database will only return those results, including all of the keywords we list and few, if any sources will use all of these keywords. What we want the database to do is return results that include at least one of the keywords from each column. In this way, the sources returned in our search could use any combination of the keywords we've listed, provided that each of our core concepts is represented. We can achieve this with Boolean operators, in particular, the words and and or. Linking two words with and has the database return results including both words. Consequently, and is best used between distinct concepts when we want our search results to relate to both. Using or has the database return results including either or both words, as long as at least one of the words is found in the record, the database will include the item in a results list. Or then is best used between synonymous and like terms when we only need to see at least one of the words in the record. In the case of our earlier search strategy, an effective search string using these Boolean operators would look like this. In many databases, you may notice that multiple search lines are provided, and Boolean operators can be selected from drop-down menus. In this case, enter a core concept and it's like terms on each line. Within a line, the terms are combined with or. The lines are then combined with and. This has the database do what we needed to do, which is to return results that include at least one of these words, one of these words, and one of these words. If you're entering your whole search into a single box, be sure to enclose each set of terms in parentheses to ensure that the database understands your logic and carries out the search correctly. This is called nesting. Another kind of Boolean operator, which is used less often, is not. Not has the database remove results that include a particular word. This can be a quick way to remove a number of irrelevant results from your search, but be careful when using it, as you can also unintentionally lose relevant results this way. Keep in mind that and and not will reduce the number of search results while or will increase them. You now know how to structure an effective search comprising multiple concepts and like terms. In other videos, we'll look at a few other helpful search techniques and tools, such as truncation, phrase searching, subject terms, and search filters.