Finding Stuff With Search Engines

Become Better At Finding Stuff With Search Engines: Boolean Search Logic Explained

by Tina Sieber

The number of websites currently in existence is unimaginable. And while – on a bad day – it only takes Google’s thousands of servers half a second to query approximately 50 billion indexed pages, it takes you significantly longer to scan only the first page of search results. On top of that, you are likely to digress and open irrelevant sites. Why don’t you do your constantly distracted and easily overwhelmed brain a huge favor and learn how toproperly construct a search?

Boolean search logic illustrated in Venn diagrams can help you visualize what you are searching for. If you think this sounds suspiciously like mathematics, you’re spot on. But don’t let that discourage you! It’s pure and simple logic, demonstrated with pretty and very simple diagrams, and so it’s easy. I promise! And I have fun examples to prove it.

The only case in which you won’t need any search logic, is when you search for only a single word, like Earth.

What Is Boolean (Search) Logic?

In a search query, Boolean logic helps us define the logical relationship between multiple search terms. The operators used to express the relationship are AND, OR, and NOT. Any number of boolean search terms can be connected with these operators to refine your search results. Let’s look at each operator separately.

OR

• search results will contain either one or several or all of the search terms
• best used when you want to pull together results on similar topics

Example: Wind OR Fire

The Venn diagram above reveals that a search for Wind OR Fire will show results for Wind, Wind AND Fire (overlapping areas), and Fire.

Example: Earth OR Wind OR Fire

Likewise, this diagram demonstrates that all boolean search terms by themselves, as well as overlapping content will be shown when connecting the terms with OR. And here is a chance to earn a Like including 5 bonus points if you can tell me who those folks in the center are.

Here are the numbers for Google’s search results for the three search terms and the OR combinations shown above:

• Earth: 1,280,000,000 results
• Wind: 909,000,000 results
• Fire: 2,090,000,000 results
• Wind OR Fire: 2,980,000,000 results
• Earth OR Wind OR Fire: 4,210,000,000

As you see, in the case of a Google search, the whole is not greater than the sum of its parts; it’s actually smaller. But since there is redundancy, i.e. overlapping areas, as can be seen nicely in the Venn diagrams above, that makes sense.

Instead of OR you can also use the vertical bar | character when performing a Google search.

NOT or rather -

• exclude keywords from your search
• best used when your search is ambiguous

Caution: While NOT is a valid term in Boolean logic, Google doesn’t appear to operate with this term. Instead of NOT, you should use the -character. Note that there is no space between the dash and the keyword you want to exclude.

Example: Wind NOT Fire or Wind -Fire

The Venn diagram above depicts the results in theory. Below are the actual numbers:

• Wind: 909,000,000 results
• Fire: 2,090,000,000 results
• Wind NOT Fire: 377,000,000 results
• Wind -Fire: 1,810,000,000
• and just for fun… Fire -Wind: 5,010,000,000 results

The numbers will vary, depending on which Google domain you are using (my browser defaults to Google.ca) and obviously they also change over time. However, the results above are nothing short of confusing. Let’s say that Google doesn’t necessarily give us all the results, so those numbers are not a reliable source of information. Looking at the first page of results, however, can give you an idea of whether or not your search worked.

Actually trying to understand the results quickly reveals that Google tends to think for you, rather than with you. For the majority of users that’s good because they don’t know what they are doing. Google appears to serve results based on its “experience” rather than the search terms and operators used in the query. This actually is a little disturbing, but good to be aware of. So let’s continue with the theory…

AND

• search results will contain all search terms
• results where one of the terms is missing will be excluded
• best used when you want to retrieve only those results where the search terms overlap

Example: Earth AND Wind AND Fire

Once more, the numbers:

• Earth: 1,280,000,000 results
• Wind: 909,000,000 results
• Fire: 2,090,000,000 results
• Earth AND Wind AND Fire: 80,500,000
• and just for fun… Earth Wind Fire: 86,800,000

At least Google cooperates with this boolean search operator. Mind you that AND typically is the default operator in search engines. So whenever you type in more than one keyword, the search engine will automatically connect them with the AND operator. Hence Earth Wind Fire in theory will yield the same search results as Earth AND Wind AND Fire.

Processing & Nesting

You can connect multiple search terms with different operators. But since Boolean logic operates based on mathematical principles, the order in which you connect your keywords will have an effect on your results. To influence your results, it helps to understand how the terms are processed. Per default, keywords are processed from left to right.

Example: Earth AND Wind OR Fire

If you want to change the order in which your keywords are processed, you can of course literally change the order. You can also enclose a set of search terms and operators in parentheses, i.e. nest them. Processing will still be left to right, but the nested elements will be treated as one unit.

Example: Earth AND (Wind OR Fire)

This result looks quite different, doesn’t it?

Conclusion

It’s generally good to know how Boolean search logic works when you are working with search engines, at least if they strictly adhere to those operators. Apparently, Google does not, meaning a simple search will often get you exactly what you need, without having to think about it. If you do want to be sure that Google does what you want it to do however, use Google’s Advanced Search. The field all these wordscorresponds to the AND operator, any of these words equals OR, andnone of these words works like NOT. Now you should be able to narrow down your searches a lot better – in theory.

If you desire to become a real power user, I recommend reviewing our article on how to master Google search operators, or how to reduce irrelevant results, or which tricks to use when you don’t know what to search for , or simply review Google’s list of search operators.

Have you ever had trouble getting Google or another search engine find what you were looking for?

Source: www.makeuseof.com