Boolean operators form the basis of mathematical sets and database logic. Using these terms to combine concepts and keywords in your search will assist you in performing a transparent, reproducible, and thorough search. Boolean operators include AND, OR, and NOT.
| AND |  |
Use AND to link ideas and concepts where you want to see both ideas or concepts in your search results. The area in blue on the diagram highlights the recall of the search when AND is used to combine words or concepts. As you can see, AND narrows the search. |
Example: "children" AND "poverty" |
|---|---|---|---|
| OR |  |
Use OR between similar keywords, like synonyms, acronyms, and variations in spelling within the same idea or concept. The area in blue on the diagram highlights the recall of the search when OR is used to combine words or concepts. As you can see, OR broadens the search. |
Example: "behavior" OR "behaviour" |
| NOT |  |
NOT is used to exclude specific keywords from the search, however, you will want to use NOT with caution because you may end up missing something important. The area in blue on the diagram shows the search results that you will get when you combine two concepts using NOT. As you can see, NOT is used to make broad exclusions. In our example, any article that discusses both "pediatrics" as well as "adults" will be excluded. |
Example: "pediatrics" NOT "adults" |
Proximity and adjacency operators allow you to search for words next to or near each other. These operators vary from database to database, so always consult the each databases's help section to find out how to use proximity and adjacency operators within that database.
Proximity/Adjacency Operators |
Example |
| "Adjacency" or "Near" Operators: Nx finds the words within x words of one another, regardless of the order in which they appear |
(healthcare OR "health care") N5 reform |
| "Next", "Precedes", or "Within" Operators: Wx finds the words within x words of one another, in the order in which you have entered them | oil W3 (disaster OR spill OR contamination) |
Selected databases and their proximity operators:
Database |
Adjacency/Proximity Operators Allowed |
Format |
|---|---|---|
| CINAHL (EBSCOhost) | Yes, "Near" and "Within" | term Nx term; term Wx term |
| The Cochrane Library | Yes, "Near" and "Next" | term NEAR/x term; term NEXT term |
| Embase | Yes, "Near" and "Next" | term NEAR/x term; term NEXT/x term |
| ERIC (EBSCOhost) | Yes, "Near" and "Within" |
term Nx term; term Wx term |
| Global Health (Ovid) | Yes, "Adjacency" | term ADJx term |
| Medline (Ovid) | Yes, "Adjacency" | term ADJx term |
| ProQuest Dissertations and Theses Global (ProQuest) | Yes, "Near" and "Pre" | term NEAR/x term; term PRE/x term |
| PsycINFO (EBSCOhost) | Yes, "Near" and "Within" |
term Nx term; term Wx term |
| PubMed (NCBI) | Yes | "term term"[tiab:~x] |
| Scopus |
Yes, "Within"* and "Precedes" *Note that in Scopus, order does not matter when using "Within," but order matters when using "Precedes" |
term W/x term; term PRE/x term |
| Web of Science | Yes, "Near" | term NEAR/x term |