Boolean Operators

The Boolean operators AND, OR and NOT describe the logical relationships between words or groups of words in a search strategy. By using your keywords in combination with these operators, you will be able to retrieve items more relevant to your topic.

The AND Operator

Using the AND operator narrows your search by retrieving only those records containing all terms. The AND operator requires that both the terms be in the same record.

Example: Searching for

atrazine AND embryo$

retrieves records that contain both “atrazine” and “embryo$.”

• Use AND to retrieve records containing both search terms: all terms must be in each record retrieved.
• Use AND to narrow your search and retrieve fewer records.
• Use AND for keywords listed in different columns of your search strategy.

The OR Operator

The OR operator broadens your search by retrieving all records which contain either or both terms.

Example: Searching for

atrazine OR simazine

retrieves records that contain either “atrazine” or “simazine” or both.

• Use OR to retrieve records containing either or both search terms.
• Use OR to broaden your search and retrieve a greater number or records.
• Use OR for synonyms.
• Use OR for keywords listed in the same column of your search strategy.

The NOT Operator

The NOT operator excludes records containing a particular term as well as records containing both terms.

Example: Searching for

triazines NOT atrazine

excludes all records that contained “atrazine.”

Note – Use NOT with caution; it may eliminate records you want.

• Use NOT to retrieve records containing the first search term but not the second.
• Use NOT to exclude certain items from your search.

Different Boolean operators can be combined in a single search statement. When entering a search statement that has both the AND and OR operators, use parentheses around the terms combined with OR, so that the computer processes them first.