Boolean operators are connector words, such as AND, OR, and NOT, that are used to combine or exclude words in a search string for more focused results.
When doing a keyword search, words can be combined using logical connectors (Boolean operators). The available Boolean operators are:
Use AND to request records that contain both words. Using AND has the effect of narrowing the search. When two terms are entered without any Boolean operator, the library catalog automatically does a phrase search. For example, if "federal government" is entered as a word search, the catalog would search for the phrase "federal government". You would get different search results if you searched "federal" AND "government".
Use OR to request records that contain either word. Using OR has the effect of expanding the search and tends to retrieve more records. For example, if "dogs or cats" is entered as a word search, the library catalog would search for either "dogs" OR "cats" in the keyword indexed fields.
Use NOT before a word or before a phrase enclosed in parentheses to exclude the word or parenthetical expression in keyword indexed fields. The Boolean operator NOT (or NO) applies only to the word or parenthetical expression which immediately follows it.
To exclude more than one word or parenthetical expression, either use parentheses or key NOT before each word to be excluded. For example, if "chess not (checkers or backgammon)" is entered as a word search (with no quotes), it would search for only those records that include "chess" but exclude "checkers" and "backgammon" in the keyword indexed fields. This example could also be entered as "chess NOT checkers NOT backgammon" (without the quotes). On Google, this NOT can be represented by a minus sign: for example "chess -checkers" (without the quotes).
Nesting involves using parentheses to ensure that Boolean operations are performed in the sequence you intend. This technique allows you to build a complex search using two or more operators (AND, OR, NOT).
BUT - You may not build a good search using more than one Boolean operator without using nesting.
Just like in Algebra, the placement of your parentheses is important in performing a search in the proper sequence. It is a good practice to always place your OR search terms together, on one line, surrounded by parentheses. For example: