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Use AND To Combine Search Words

The most useful trick of boolean algebra is to combine your search keywords with the operator AND, which ensures that the web pages returned include all of those keywords. This lets you search for several keywords at once to narrow down your search to just the most relevant content.

While some search engines assume the AND function by default if you just list keywords all in a row, others will consider some of the words optional, some will combine the keywords with the OR operator instead, and others apply different optimization rules that can lead to unpredictable results. If not sure, use the site's advanced search function and find out how to ensure your keywords are all considered mandatory -- combined with AND.

To illustrate the numerical advantage of the AND combination over the OR combination, consider the difference between the results returned by the searches "mozart or biography" and "mozart and biography".

  • mozart or biography. The search engine finds pages that include the word "mozart", then finds the pages that include the word "biography", and then returns the union of the two lists -- all of the pages that contain the word "mozart" or the word "biography".

  • mozart and biography. The search engine finds pages that include the word "mozart", then finds pages that include the word "biography", and then returns the intersection of the two lists -- only those pages that include both of the words.

The results of searches on Alta Vista (historical) and Google listed below show that the AND search returns many times fewer pages than the OR search, making it that much more focused and useful.

Search Query

Jul 2000
# of Pages
Alta Vista

Dec 2004
# of Pages
Google

mozart

425,747

7,900,000

biography

3,026,098

50,000,000

biography OR mozart

3,306,047

* 27,100,000

biography AND mozart

16,145

276,000

* Approximation returned by search engine;
unknown why less than for "biography" alone.

NEAR. The Alta Vista search engine used to be the only Internet search engine that also supported an interesting search innovation, the NEAR operator, which was like the AND operator in that both operands had to be present, but with the added condition that the terms must also be "near" to one another, which Alta Vista defined as within ten words. In practice, that usually meant they were in the same or adjacent sentences, producing a very tight correlation between the search terms.

While Alta Vista still supports the NEAR operator for backward compatibility, it appears to have incorporated the concept into the AND operator, since they both return the same number of results. Hopefully someday this useful operator will make a return on a major search engine, since it was particularly useful when you received a lot of pages with the right keywords but wanted to ensure they were all within the same sentence of two.

For example, the author once was looking for Winston Churchill's middle name, but found that the following search did not return pages where the two phrases were sufficiently related:

"winston churchill" AND "middle name"

On the other hand, use of the NEAR operator returned pages where the two phrases were used in the same sentence, which provided several hits in the top ten where Mr. Churchill's middle moniker could be readily found:

"winston churchill" NEAR "middle name"

 

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