booleans
1 2018-06-20T17:55:58-07:00 Elizabeth Christian d68b58b056fd4bd35e7e15a02d90ff0dd450aae9 30651 1 The Boolean operators AND, OR, and NOT exclude or include subsets of sources. plain 2018-06-20T17:55:58-07:00 Elizabeth Christian d68b58b056fd4bd35e7e15a02d90ff0dd450aae9This page is referenced by:
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Search Statements
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At this point in your search process, you are moving from merely identifying main concepts and similar search terms to developing more complicated search statements that can do more precise searching.
Use Quotation Marks for Phrases
Put quotation marks around any phrases among your terms so that the phrase is what’s searched for, rather than the separate words. “Common cold” instead of common cold is a good example. Without those quotation marks, just think how many sources Google or other search tools would waste their/your time on things that have nothing to do with our sniffles.
Use Wildcard and Truncation Symbols to Broaden
Consider whether using wild card or truncating symbols would help find variations of a word. For instance, the wildcard symbol in wom?n finds both woman and women, and the truncating symbol in mathematic* finds mathematics, mathematically, mathematician, etc.
Consider AND, OR, NOT
You can often do more precise searching by combining search terms by using the words AND, OR, and NOT. These are known as Boolean Operators. Generally, using these operators narrows your search, making it more precise.
AND – If the main idea contains two or more ideas, you’ll want to use AND to combine those terms in your search statement. To look for information about spiders as signs of climate change, you’ll want to have both terms in the search and perform an AND search. That’s what automatically happens in search engines like Google unless you tell them to do something different by using OR or NOT.OR – If the main idea has several synonyms, use OR to combine them. Most search tools search for all terms (AND) by default, so you need to use the term OR between terms to let it know you want to find any of the terms not documents with all the terms. For instance, in the previous example of Latino small business growth, we would want to also use the term Hispanic.
NOT – If the main idea has a common use you want to exclude, use NOT to exclude that word. For example, if we were looking for information about illegal drug use we would want to exclude prescription drugs from the search results. This is commonly done with NOT or the use of the minus (-) sign. In Google, to exclude a word, put the - character in front of it like this: -prescription, without spaces.
Using Parentheses with Multiple Operators
When a search requires multiple Boolean operators (AND, OR, NOT, or their symbols), you must use parentheses to group the appropriate terms and quotation marks with each Boolean operator. The resulting statements connect terms, remove terms, and organize search terms in ways that result in complex and precise searching. The use of parentheses may remind you of PEMDAS, the order of operations used you learned in math courses.
Being skillful at this task of envisioning the effects Boolean operators have on a search can help you troubleshoot your own search statements when they aren’t turning up what you expected.
Example: “United States” AND (immigration OR emigration)
Can you tell that the searcher wants to find information about the United States’ immigration or emigration?
The searcher will find more with this arrangement than would turn up if the statement had been “United States” immigration emigration. That’s because the latter arrangement without parentheses would find only information that was about both United States immigration and emigration, instead of either.
Example: (cats OR dogs) AND (treatment OR therapy)
Can you tell that the searcher wants to find information about either treatment or therapy for either cats or dogs?
That’s a different search from what the searcher would have gotten if this statement had been used: cats dogs treatment therapy. Anything found with the latter statement without parentheses would have had to be about both— not just either—therapy and treatment for both—not just either—cats and dogs. So the latter statement would have turned up fewer pieces of information.