When you are dealing with computers, you are always dealing with calculators. Boolean commands (or operators) tell the system what to do with your keywords and synonyms.
AND, OR and NOT are the most common Boolean commands, and are used in almost every search tool (even if it isn't obvious at first - like the invisible AND in Google).
There are other Boolean commands, but these three are the ones you'll always use.
Note the use of capitals: AND, not and. OR, not or. NOT, not not.
This helps the computer know you mean to use the word as a command, and not as a real word (most search tools won't look for the words and, or and not, as they appear too often in texts)
Remember "BODMAS" or "BOMDAS" in maths? How the brackets told you which part of a sum should be done first? (2 + 5) x 6 = 42, but 2 + (5 x 6) = 32.
Boolean commands can have a similar effect on your search results.
You can create more complex search strategies using Parenthesis. For example: Ice-cream AND (Chocolate OR Vanilla)
Searching for exact phrases using Inverted commas can also provide a more accurate search result. For example: "chocolate ice-cream"
Truncation symbols such as * and ? can be used to find words with the same root, so that plurals and other variations of a word are included. For example: A search for sweet* finds sweets, sweetener, sweeter etc.
Be aware of spelling variations between British and American English and try alternatives in your search sets. For example: colour OR color
If you are using a database or catalogue with a guided search (or multifield search - in other words, separate boxes for each of your search terms), then you just need to think about which boxes to use for your terms. But, if it only has one search box, you will need to construct a Search Statement.
This is when you put all of your phrase searching, Boolean terms and trunkation together to make one "sum".
You can find examples all over this page, but here are a couple to give you an idea of what a search statement might look like:
"pain management" AND ((complementary OR alternative OR natural) medicine*) AND herb*
chemotherap* AND interact* AND (antihistem* OR "histamine antagonist" OR "histamine antagonists")
You now creat a "sum" using your keywords and synonyms:
The words are the "numbers" in your sum, the Boolean commands are the "operators" (+, /, -).
AND (+) allow us to narrow our search.
example: malaria AND mosquito*
OR (/) broadens our search
example: obes* OR overweight OR "over weight"
NOT (-) excludes a term we don't want
example: radiation NOT nuclear
AND: finds records that contain all the keywords words specified. It is the most common operator and many search engines use it as a default setting. Strawberry AND Vanilla AND Chocolate retrieves all the records that contain Strawberry, Vanilla and Chocolate. It narrows your search.
Some search tools will accept a + (plus sign) instead of an AND.
Remember: AND (+) will give you fewer results - only the articles/pages with both (or all) search terms.
OR: finds records that contain either or both of the words specified. It is useful for finding synonyms or where different words are of equal value in your search.Strawberry OR Chocolate OR Vanilla retrieves records that contain either or all Strawberry, Chocolate and Vanilla. It broadens your search.
Some search tools will accept a / (forward slash - used on computer keyboards for divide) instead of an OR.
Remember, OR will give you more results - anything with either (or any) of your search terms.
NOT: finds records with only the first two of the three terms. (Strawberry OR Vanilla) NOT Chocolate retrieves records with Strawberry and/or Vanilla but excludes those records containing Chocolate. It narrows your search but should be used with care as it can easily exclude relevant results.
NOT makes sure any page with this term will not turn up in your results list - it is used to get rid of results you don't want.
Some search tools with accept a - (minus sign, or hyphen) instead of NOT.
Use this one carefully, and make sure the word you are excluding will not be used in articles or pages you actually want.
So, if you wanted to find results about pirate ships, but didn't want results about ships used for pirate radio broadcasts, you could write:
(pirate* AND ship*) NOT radio.
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