Boolean Searching

Introduction to Boolean "operators"

When searching a database, first think of keywords that best describe your topic. Then combine these keywords using Boolean "operators" to broaden or narrow your search.

The Boolean operators are:

and

or

not

They determine how the computer searches for your keywords, and what information is returned to you.

and:

The "and" operator tells the computer to search the database for every entry or record that has each of the words somewhere in the same entry or record. For example, if you want information on education in Ontario, you might search the appropriate source in this way:

Ontario and education

As illustrated in the above diagram, the computer goes through its database and first retrieves every record it finds with the word Ontario and every record with the word education. It then combines the searches, and gives you only the records in which both words appear somewhere in the same record. This is a way of narrowing a search and making it very specific.

or:

The "or" operator tells the computer to search the database for every record which has any of the words specified. Both words do not have to occur in the same record. For example, if you want information on either stress or anxiety, you might search the appropriate source in this way:

stress or anxiety

As the above diagram illustrates, the computer then goes through the database and retrieves every record with stress, and every record with anxiety. This results in a very broad search.

not:

The "not" operator allows you to remove a word from your search. It tells the computer to search for every record with your first word, and remove any record which also contains your second word. For example, if you wanted information about sleep, but not sleep apnea, you might search the appropriate source in this way:

sleep not apnea

As the above diagram illustrates, the computer goes through the database and retrieves every record with the word sleep. It then removes any of these records which also contains the word apnea, and gives you only those records with sleep, not sleep apnea. The not connector thus narrows your search.

Proximity

It is sometimes useful to specify that words appear close together. In a sense, this is a more restricted version of the Boolean operator "and". It is particularly useful when searching a full text database, since if you searched fulltext using "and", your first keyword might be on page 1 of an article and your second keyword on page 20, resulting in a search result which is not relevant to your topic. Proximity operators vary in name, function and execution.

Phrase searching :

This is the most restrictive type of proximity operator. You specify that the keywords will appear beside each other in the specific order. For example, employment equity. Depending on the database, the phrase may have to be enclosed in parentheses.

Adjacency:

The abbreviation ADJ is often used to denote that words must appear side by side, but in no particular order.

Within, near, W/x :

These specify that the words must appear within no more than x number of words. Depending on the database, the user may be able to specify the number of words, or the search interface may set a default number.

Truncation / wildcard symbols:

Truncation or wildcard symbols allow you to search for a root word and all of its various endings, or variant spellings. The symbols vary in depending on the database, but are usually *, ?, or ! Truncation symbols are usually used at the end of words, but in some databases can be used within words. For example, design* would retrieve all words with the root design and any other endings, such as designs, designing, designed, designers, etc., wom?n would retrieve all records with women or woman.

Boolean Search Strategy

Planning a Search

1. Identify the concepts in your search.
2. Think of synonyms and alternative ways of expressing each concept.
3. Arrange synonyms for the same concept in a group.
4. Connect your synonyms with "or"s, and place in parentheses.
5. Connect your concepts (or groups of synonyms) with "and"s, "not"s or proximity operators.

For example, if you are looking for information on liquor laws in Ontario and Quebec, you might search as follows:

(alcohol* or liquor or spirits) and (law* or legislation or licens*) and (ontario or quebec)