Boolean Searches

Boolean Logic
More elaborate searches can be constructed by creating Boolean search strategies that combine terms using the connectors AND, OR, and NOT.

Combining Terms Using "AND"
If you enter two or more search terms, Google automatically combines them into a Boolean "AND" search that matches only pages where all search terms are present. Enter the three keywords from the sample question in the Google search box. The total number of pages matched by this search will be less than in the first search for "eclampsia" alone.

Combining Terms Using "OR"
A Boolean "OR" search matches pages where at least one of the selected terms is present. In Google, the word OR must be capitalized. Some web pages relevant to our question use the term "eclampsia", while others use the terms "preeclampsia", "pre-eclampsia" or "toxemia". A search strategy that would match all these terms is "eclampsia OR preeclampsia OR pre-eclampsia OR toxemia". Another relevant search phrase is "diabetes OR diabetic".

Combining Terms Using "NOT"
A Boolean "NOT" search matches pages which mention one term but excludes any of these pages which mention the NOT term. To find pages that mention "eclampsia" but exclude pages which mention "diabetes", the Boolean phrase is "eclampsia NOT diabetes". In Google, "NOT" is represented by a minus sign, so enter "eclampsia -diabetes".  The minus sign immediately precedes the exclusion word, with no intervening space.

Phrase Searching & Stop Words
To search for an exact phrase, such as "gestational diabetes" enclose it in quotation marks. Another common phrase relative to our question is "diabetes in pregnancy". Do a quoted phrase search for these three words. Google will give you a message that "in" is a common "stop word" and has been ignored. To force the program to search for the exact phrase including the stop word, enter a plus sign immediately before the word "in" ("diabetes +in pregnancy").

Too Much Information
If you find too much information, narrow your strategy by adding more search terms or making your search terms more specific.

Too Little Information
If you find too little information, use fewer search terms or more general terms.