Searching: AND, OR and NOT
In the BCU Library Search box and in many databases, you can insert AND, OR and NOT between the search terms.
AND, OR and NOT are called Boolean operators. They add logic between search terms and each one has a different purpose:
Other search engines and databases may use the same elements slightly differently.
AND: specify required terms
The AND operator requires the search engine to retrieve documents that include all the search terms.
Example: obesity AND diabetes AND diet
➡︎ This search returns documents that contain all three keywords, obesity diabetes diet, in no specific order.
Some search engines, like Google, assume the spaces between search mean AND.
However, many library databases require you to specify how you want to search so it's good practice to use AND.
OR: combine multiple terms
The operator OR tells the search engine to select any item that contains any of the search terms.
Example: blueberries OR strawberries
➡︎ This search returns the documents that contain blueberries and those that contain strawberries.
There are some words which generally mean the same thing. i.e.: adolescent OR teenager
Others are perhaps dialect/country based. i.e.: trousers OR pants
You may also want to combine some broader but related concepts this way, if you don't mind which of the concepts is included. i.e.: fantasy OR horror OR science fiction
NOT: exclude unwanted terms
NOT excludes items that contain the specified keyword from the results.
Example: Cheddar NOT cheese
In this example we want to search about Cheddar, the village in Somerset, not the cheese that is named after it.
➡︎ This search returns documents that contain Cheddar but not those that contain cheese.
If you suggest a common word to exclude, you may find your results become too limited and miss some important research.
Make sure to run the search without NOT so you are aware of what you are missing.
Using NOT is a bit like picking out a particular colour from a packet of sweet. i.e.: smarties NOT red
It allows you to be more specific with your subject search and avoid resources associated with the same keyword but are about a different topic:
- art nouveau NOT Rennie Mackintosh
- primary NOT maths
In Google, NOT can be represented with a minus sign (-). The search Jaguar speed -animal will exclude references to the speed of the animal Jaguar.
You can also mix multiple Boolean operators to create even more precise queries.