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Planning a Database Search

Planning a search is a combination of problem-solving skills and basic technical skills. This guide takes you through the basic steps that will help you plan an efficient and effective search.

Implementing your Search

To prepare your search plan you need to understand how to structure your search so that you can input it into a database. This section takes you through Boolean Searching, Truncation, Adjacency and using Phrases.

Boolean Logic - AND OR NOT

Boolean Logic - AND OR NOT

You need to link concepts and keywords together in a way that a database can process. You do this using the Boolean Logic - AND OR NOT.

  • OR groups words together that have the same or similar meanings. For example, prehospital OR paramedic* OR ambulance finds all articles that contain one or more of these terms.
  • AND compares sets of journal articles and only displays those that contain all the terms in each set. For example, prehospital AND analgesia finds only articles that contain both terms.
  • NOT excludes terms from your search. For example, Ketamine NOT Morphine finds only articles that contain the word Ketamine and does not find any articles that contain the word morphine even if the word Ketamine is present.

Need some more help.  Have a look at this animation on using OR/AND.  Note YouTube may be blocked on some NHS Computers. 

Using Boolean Logic

The most effective way to organise your Boolean search terms is to use the Concept Block approach. This means using Boolean OR to group the keywords for each Concept together into a single group or Set before combining the Sets using Boolean AND to find articles that contain both sets of terms. 

For example, to find all the articles around the Concept of prehospital we could type:

prehospital OR paramedic OR ambulance OR EMS OR emergency medical service

building a set of articles around the idea of prehospital.  To find articles on the Concept of Ketamine we could type: 

Ketamine OR analgesic OR pain management OR pain relief

Typically databases will assign each Concept a number. For example Set 1 for the prehospital and Set 2 for Ketamine. To complete the search using the Concept Block approach we would type

1 AND 2

An alternative way to do this is to group the OR'd terms together using round brackets.  This tells the database to process the OR'd terms first before AND. It has the advantage of being able to type the whole search out as a single string of characters.  The disadvantage of this though s that if you want to change the search and run it again you have to type the complete search out each time. This approach would look like this:

(prehospital OR paramedic OR ambulance OR EMS OR emergency medical service) AND (Ketamine OR analgesic OR pain management OR pain relief) 


Truncation is a technique to help you to search for words that have multiple or plural endings. It uses the * character sometimes called a wildcard. If you want to search for paramedic or paramedics you should type paramedic*. If you want to search for analgesic, analgesia or analgesics you should type analges*. This finds all words beginning analges whatever the ending. Thinking about our search using truncation, the keywords would now look like this:

Concept 1  Concept 2  Concept 3 
prehospital  Ketamine recent 
Keywords Keywords Keywords
prehospital Ketamine  2007-2018
paramedic* analges*   
ambulance* pain management   
EMS  pain relief   
Emergency Medical Service    


Using Boolean AND allows you to combine words together, pain AND management but finds these words anywhere in an article record even if they have no relationship to each other.  For example pain in the Title and management in the last sentence of the Abstract.  Adjacency commonly expressed as ADJ allows you to express a relationship between words. For example pain ADJ management returns results where the selected keywords are within one word of one another in the specified order i.e. "pain management" but not "management pain". 

You can also express the number of words to occur between the terms you use.  For example, pain adj5 management finds the term within the five words of each other in any order. Roughly in the same sentence.

Note the implementation of Adjacency in different databases. Check the Help Pages for the Adjacency Terms and their effects. 


In some instances, concepts or ideas cannot be expressed as a single keyword, for example, Emergency Medical Services or chronic renal failure. Most databases will treat these as phrases and search for exact examples of those phrases in the database. Some, like NHS Evidence, require you to put them in parenthesis, for example, "Emergency Medical Services".

Thesaural Terms and Filter

Thesaural Terms are terms applied to each article record from a Thesaurus like MeSH where the topics of each article are substantially about the topic of the term.  For example, the thesaural term most relevant to the prehospital care is "Emergency Medical Services". Searching for "Emergency Medical Services" as a thesaural term finds all the relevant articles in the database on that topic. 

It's actually a bit more complicated than this, however, most common Concepts such as the idea of prehsopital care have filters or preplanned searches you can copy and paste into your search.  You can find a search filter here

Writing out your search

You are now in a position to write out your search using some or all of these techniques. The search strings in the example would look something like this:

prehospital OR paramedic* OR ambulance* OR EMS OR "emergency medical service"


Ketamine OR analges* OR (pain ADJ2 manage*) OR (pain ADJ relie*)