Boolean searching

Boolean searching is method of combining two or more search terms to increase or restrict the amount found by a search in a catalogue, database or search engine. The three main commands are OR, AND and NOT.

Using OR

You can combine multiple terms into one search to get more records or "hits". You do this by using the Boolean operator OR. Most databases offer Boolean searching.

For instance, if you type in itch or scratch the search engine in the database will find all the records that have either of these words or both words in them. So you should get quite a lot of hits.

Boolean is library terminology (derived from mathematics). All you need to know is that Boolean searching allows you greater control over the way that you search.

Using AND

You can combine your search terms to try and limit the amount of material or "hits" you get, or to make them more specific to your search. To do this you can use a Boolean operator, AND.

The AND operator is used to reduce the number of hits you get. When you use AND the search engine only returns records that have all the specified terms in them. For instance if you use fish and chips the database engine will only return records with both the word fish and the word chips in them.

Using NOT

You can combine your search terms to try and limit the amount of material or "hits" you get, or to eliminate irrelevant terms. To do this you can use a Boolean operator, NOT.

The NOT operator is used to reduce the number of hits you get. When you use NOT the search engine only returns records that do not have any terms that you do not want in them. For instance if you use music not jazz the database engine will only return records that have the word music but do not have the word jazz in them.

Use with care as you may be eliminating useful records. In the example above you would miss out on records that have information about types of music including jazz.

NOTE: in some search engines and databases you need to type AND NOT to achieve this.