Search Processing Order
Databases usually process the Boolean operators in a logical order.
They typically recognise AND as the primary operator and will connect concepts with AND together first.
If you use a combination of AND and OR operators in one search, use parentheses (brackets) to groupthe OR words together so that your search is processed correctly.
For example:
If you wantto find information on cloning humans and cloning sheep, use the following instruction:
cloning AND (sheep OR human) - This will search for cloning AND sheep as well ascloning AND human
If you donot use the parentheses and searchusing the following:
cloning ANDsheep ORhuman,your search will be processed as:
- cloning AND sheep as one search
- OR human as a secondary search - This means that your search results containing human would not be linked in any way to cloning.
Many databases offer the functionality to separate out your search terms, and this saves you having to add the parentheses. Sometimes you will have to access the Advanced Search for these options.
In this example from the Web of Science database, you can use the Basic search form to add multiple search lines by clicking on Add Another Field.
