Module 2:
Mixing Boolean AND and OR in Keyword Searches |
©2020 by Chris Niemeyer, University of Missouri-St. Louis.
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As you have learned, Boolean and narrows keyword searches. This makes it very powerful.
Let's say you were interested in finding books on a particular aspect of psychology. ![]() Screen2 |
You type the keyword psychology on the search line, as in the example below.
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Most library catalogs will have quite a few books that mention psychology. You might get tens of thousands of hits.
Maybe, depending on the size of the library, you might even retrieve several hundred thousand records. ![]() Screen4 |
Let's say you were interested in psychology as it relates to creativity.
Using and, the example below would be useful since every record would have to deal with both topics to some degree. ![]() Screen5 |
Let's assume that you are also interested in the psychology of creativity and the role of friendship in the process.
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You would, of course, add the extra term with and.
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Finally, let's say you were interested in how this process affects those involved with music.
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You would also add the new term with and.
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At this point, the number of books retrieved by this search should be much smaller than if you had merely searched for
psychology and creativity.
Boolean and requires that ALL keywords be present in the same record. With each use of and below, the search became progressively more exact. Sometimes you need this exactitude. ![]() Screen10 |
In contrast, exclusively using Boolean or
as shown below would have been a disaster. The search would retrieve too many books, and most of them would have little or nothing to do with each other.
If Boolean and is too exact, Boolean or is too expansive. ![]() Screen11 |
Actually, there may be times when you will need to be expansive as well as exact. We will show you what we mean....
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Let's say you need articles about artists, and the experience of separation from one's country.
Exile is one example of such an experience. ![]() Screen13 |
You perform a keyword search using Boolean and.
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The search could be duplicated with the "Advanced Search" screen of many library databases.
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An "Advanced Search" screen usually contains two or more search lines.
Notice that Boolean ![]() ![]() ![]() ![]() Screen16 |
Every record that you retrieve will now contain the terms artists and exile.
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Let's say you didn't retrieve enough records with these keywords.
What else could you do? ![]() ![]() ![]() Screen18 |
Painters are artists. So you can add this keyword to the search using Boolean or.
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Remember, Boolean or ensures that the two terms below will be equally sought after.
As long as a record contains just one (or both!) of the two terms, it will be selected. Boolean or is thus very expansive! ![]() Screen20 |
The expanded search should now provide more hits.
What if you still need more search results ... what else could you do? ![]() ![]() Screen21 |
Well, sculptors are also artists, so add them to the search.
You will likewise use Boolean or to do this. ![]() ![]() Screen22 |
You could do the same with other kinds of artists, like musicians
or writers.
musicians
writers
or
or
Just keep separating the terms with Boolean or. ![]() ![]() Screen23 |
Enough about the artists. What about the concept of exile? That is just one type of separation from one's country. ![]() ![]() Screen24 |
Creative people might live in another country because they want to, which makes them "expatriates". Or they might flee their homeland because of danger, so that they become like refugees.
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You could also add these terms to your search with Boolean or.
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And what if you were interested in the experience of artists separated from their country as revealed in letters or correspondence or diaries?
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If there was a third search line available, you could also add these new terms to your search.
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We are using the open-ended qualities of Boolean or to expand relevant keywords.
Then we are progressively narrowing search results with Boolean ![]() ![]() ![]() ![]() Screen29 |
For this search, as long as a record contains just one of each term on the three lines below, it will be relevant.
So an article about musicians in exile and their correspondence will be of interest to this topic. ![]() ![]() ![]() Screen30 |
Likewise, a record about artists
who are expatriates
and their diaries
will also be of interest.
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Some might say this is taking searching too far.
That depends. If you are having difficulty researching a topic, then doing something like the below would be very useful. ![]() ![]() ![]() Screen31 |
Conversely, a search like this one, with only three good keywords, would retrieve fewer hits.
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Whether you want to expand then narrow your search with Boolean or and ![]() Just remember: it is something you can easily do with the "Advanced Search" feature of most library databases. ![]() ![]() ![]() Screen33 |
Also, whether you use Boolean operators or not, ask for help from a reference librarian if you are having trouble finding information.
Your reference librarian will be more than happy to help! :-) ![]() ![]() ![]() |