Searching with AND, OR, NOT

When you enter terms in a database or library catalogue keyword search, you need a way of showing the relationship between the terms. A search using the terms 'forests' and 'fires' could be a search for everything on forests and everything on fires or it could be a search for everything on fires in forests - a much smaller result. You need to tell the database which you want.

Most databases use the standard operators or or and or not to link terms (Boolean operators commonly met in other science contexts) e.g. (fire or burning) and (vegetation or forest or bushland). Where a search form with drop-down boxes is provided, databases may use the labels any of these or all of these to link terms.

OR

broadens a search, giving citations which include either one term or the other. This is equivalent to the drop-down box label any of these. e.g. fire or burning gives citations that include fire, and citations that include burning, and citations that include both. The operator or is likely to be used between synonyms, alternative, narrower or broader terms which represent aspects of the same concept.

AND

restricts a search, giving citations which include both terms. This is equivalent to the drop-down box label all of these. e.g. fire and vegetation gives only citations that include both the terms fire and vegetation

NOT (sometimes AND NOT)

excludes citations containing terms you do not want e.g. vegetation not grassland
Use not as a last resort because you are likely to throw out the baby with the bathwater. In this case, any citations containing both vegetation and grassland will also be excluded.

BRACKETS

group terms linked by OR, when both AND and OR are present in a search statement.
e.g. (fire or burning or wildfire) and (vegetation or forest or bushland)

PHRASES

are searched in different ways in different databases
e.g. in quotes - “french revolution”; as adjacent terms without an operator; through a drop-down box labelled as a phrase. Check database or catalogue help screens for details.

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