Database search tips

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Understand the difference between keyword searching and thesaurus searching

Keyword search

A keyword search will only search in certain indexed fields such as the author, title, subject heading and abstract fields. These may differ between databases. If your search term is not contained in one of these fields then some relevant articles will not be included in the search results.

Your search will only retrieve results based exactly on the terms entered. For example, a search for cardiac arrhythmias will not retrieve other forms of the word including synonyms, singular/plural, one word/two words/hyphenated, or British/American spellings. This can produce a lot of irrelevant search results, for example an article may mention these terms but overall it may not be relevant to your topic.

Thesaurus search

A thesaurus search means you are searching for specific database terms that describe the concept of your topic, and will retrieve synonyms as well. This produces precise and relevant results, allowing you to retrieve all items in the database on your topic. Always use thesaurus searching when available.

You can access the thesaurus in PubMed by using the MeSH option from the drop-down menu or the MeSH Database link under More Resources.

Ovid databases automatically map to the thesaurus (for RCH users).

For Ebsco databases, use the tabs at top of the search screen: CINAHL headings (for CINAHL); Thesaurus (for ERIC) and MeSH (for Medline).

Search one concept at a time

Divide your search question into individual concepts, and then search each concept separately.

Search question: Management of cardiac arrhythmias in the Emergency department

Concept 1: cardiac arrhythmias

Concept 2: Emergency department

Use wildcard truncation for keyword searching

The wildcard truncation symbol is usually an asterisk (*) but can differ between database; always check the Help information in each database.

In PubMed, Ovid and EbscoHost databases, the asterisk (*) is used to find all different word endings. For example, emergency department* will retrieve emergency department or emergency departments. Similarly, a search for arter* will find artery, arteries or arterial.

Truncation should only be used for keywords; never apply truncation to thesaurus terms.

Boolean AND versus Boolean OR

Combine different concepts using AND. For example cardiac arrhythmias AND emergency department will retrieve articles containing both search terms.

Combine similar concepts using OR. For example emergency service, hospital OR emergency department* will retrieve articles containing either term.

Use filters to limit search results

A filter is a separate search strategy that can be applied to your own search to limit results.

A range of filters have been saved in the Ovid platform for your convenience, such as Developing countries, and Refugees. Log into your Ovid personal account to access these and other filters.

Filters are database specific, so use a Medline filter in Medline only, Embase filter in Embase only, etc.

Contact the Library to get help in learning to apply filters to your search.

Explode thesaurus terms to broaden your search

When searching using thesaurus, include narrower terms if relevant.

In Medline/PubMed, the thesaurus (MeSH) term for cardiac arrhythmias is arrhythmias, cardiac. Exploding this term will increase your search results by including arrhythmia, sinus; atrial fibrillation; atrial flutter; bradycardia; Brugada Syndrome; cardiac complexes, premature; commotio cordis; heart block; Long QT Syndrome; parasystole; pre-excitation syndromes; tachycardia; ventricular fibrillation; and ventricular flutter.

By not exploding, results are limited to articles containing the thesaurus term arrhythmias, cardiac, not the more specific types of cardiac arrhythmias.

In Ovid and EbscoHost databases you must choose to explode the term; in PubMed the term is exploded by default.

Focus thesaurus terms to narrow your search

You can Focus a thesaurus term in your search to reduce the number of results. When Focus is applied the thesaurus term becomes a major term, that is it becomes the main point in the paper.

For example, focussing the thesaurus term arrhythmias, cardiac will only find articles where cardiac arrhythmias are the main subject.

Applying focus will limit retrieval, so you should use it only at the refining stage of your search, not at the initial stage. It can only be applied to thesaurus terms, not to keywords.

The terminology for focus in Ovid is Focus; in EbscoHost it is Major Concept; in PubMed it is Restrict to MeSH Major Topic.

How to delete search lines

You can delete search lines you don’t need from your Search History by selecting the line number followed by Remove (Ovid); Delete Searches (Ebsco); Delete from History (PubMed); or the “minus” icon (Cochrane Library).

In Ovid, you can also enter the following command in the search box: n, where n is the line number(s) to be deleted. For example, to delete the first three lines of your search history, type 1, 2, 3 or 1-3. To delete your entire search history, use all.

Warning: use this command wisely; deleted search lines are not recoverable!

Save your search history

Saving your search as a Permanent search allows you to continue working on it later. You can also save it as an AutoAlert to receive regular updates on your topic.

This feature is available for all registered users of Ovid, Ebsco, Cochrane Library, and PubMed databases.

Using the ADJn proximity operator in Ovid

Use the ADJn proximity operator when you are unsure of the exact phraseology used in the literature.

For example, (survival ADJ2 rate).mp. will find terms in any order and with one word (or none) between them. The search will retrieve: survival rate; rate of survival; survival (PFS) rate; survival (OS) rate, etc. The higher the value of n, the greater the retrieval.

ADJ can be applied without a number, e.g. (survival ADJ rate).mp. In this instance, it is identical to “survival rate”.mp. Without the n, the search is directional; the word survival must come before the word rate.

This applies to keyword searching only.

Age Groups and Humans limits

When limiting your search to any Age Groups do not limit to Humans as well. (In Ovid this option is located in the Additional Limits options; in Ebsco databases find it by using the Edit link in your search history.)

The Age Group tags refer only to humans, so papers containing an age group must have the tag Humans. Papers containing the tag Humans do not necessarily have any Age Group tags; if the author did not list the age for the human subjects, no age group tags will be assigned.

When using thesaurus terms that are already age-specific, for example child development/ or arthritis, juvenile/, do not limit to Age Groups.

Check the year of entry for MeSH terms

MeSH (Medical Subject Heading) terms are updated annually so it is important that you check the year of entry for each term to see if it is current and valid at the start year of your search.

Details of the MeSH term including Year of entry is found in the Scope (denoted by the “I’). For example, in the Scope for Autism Spectrum Disorder, the Year of entry is 2016 and Previous indexing terms are Child Development Disorders, Pervasive (2010-2015).

Therefore, using the MeSH term Autism Spectrum Disorder will only retrieve items from 2016 onwards. To find literature before 2016 you must add the MeSH term Child Development Disorders, Pervasive to your search.

An alternative to using the Age Groups tag

Most databases have a limit for Age Groups, such as All Child (0-18), available from the Additional Limits option. In most situations this is sufficient in reducing the search results to that particular age group.

In a systematic review it may not be sensitive enough to capture all relevant articles for this age group. Instead, consider limiting your search to keywords that describe your age group, e.g. in Ovid databases, use:

(newborn* OR neonat* OR infan* OR pre-schooler* OR preschooler* OR child* OR adolescen* OR pediatric*1 OR paediatric*1 OR youth*1 or teen or teens or teenage* or teen-age*).af.

Note: .af. searches all fields in the database.

An expanded version of this is available as a filter which you can apply to a new or existing search. See the tip 'Ovid search filters'.

Field searching in Ovid

Limiting your keyword search to certain fields is an effective method for reducing search results. First, find the field code (abbreviation) supported by the database. In Ovid, you'll find this in the Search Fields tab (located above the search box).

Examples of field searching

These example searches will find the phrase “third world” in the Title & Abstract, Keyword Heading, Candidate Term and Subject Heading fields respectively:

  • Medline (Ovid): (third adj world).tw,kf,hw.
  • Embase (Ovid): (third adj world).tw,kw, dq,hw.
  • APA PsycInfo (Ovid): (third adj world).ti,ab,id,hw.

Edit your saved search in Ovid

Display your search in Edit mode:

  1. Go to My Workspace and log in
  2. Select My Searches & Alerts
  3. Select the Edit tool

Now you can Edit or Delete individual lines, and Insert additional lines. Submit changes for each line then Save.

Use subheadings to narrow your search

You can restrict the focus of your search by limiting MeSH terms to specific subheading(s) only.

For example, to find articles on the use of all bronchodilator agents in treating respiratory disorders, limit the MeSH term bronchodilator agents to the subheading tu (therapeutic use).

In Ovid Medline, the search line becomes: exp bronchodilator agents/tu.

Use floating subheadings to broaden your search

Floating subheadings (fs) are subheadings that are not attached to any particular thesaurus term and are used to broaden a search.

For example, to search for the epidemiology of diseases in developing countries, you can apply the subheading ep (epidemiology) to various thesaurus terms that describe diseases such as Malaria/ep; HIV Infections/ep; Diarrhea/ep; etc.

Unless you can include ALL the disease thesaurus terms, a sensible approach is to search for the epidemiology floating subheading: ep.fs. This will retrieve any papers that contain the subheading ep (epidemiology) regardless of the thesaurus term in front of it.

Each thesaurus term has different subheadings. Subheadings are database specific, for example: the subheading 'ab' (abnormalities) in Medline does not exist in Embase.

Explode thesaurus term to increase results

Expand your search by using explode on the thesaurus term to include that term plus narrower terms in your search results.

For example, in Ovid Medline, a search using the MeSH term “asthma” alone (asthma/) retrieves a large result set. Exploding that term (exp asthma/) retrieves many more results.

These results now include the narrower terms: asthma, aspirin-induced; asthma, exercise-induced; asthma, occupational; and status asthmaticus.

You can chose to include some or all the different types of asthma. Don’t explode if the narrower terms are irrelevant.

Explode can be applied to a thesaurus term only, never to a keyword.

Ovid stop words

Words of little intrinsic meaning that occur too frequently to be useful in searching text are known as ‘stop’ words. In Ovid, you cannot search for stop words by themselves, but they are searchable in a phrase. Stop words are:

about as both into on these toward which
all at by it or they upon while
among be for its that this used with
an been from not the those using within
and between if of their to what  

Ovid reserve words

Reserve words such as: and; or; not; use; adj; add; sub; and scope are processed as operators when entered as part of a query.

When enclosed in quotes, they are treated as a literal terms. For example, scope is an advanced search syntax command that automatically opens the actual scope note (term definition). To use it as a search term and not as a syntax command, enclose it in quotes, for example "scope of nursing practice".

Cochrane Library: how to manually add search lines to Search Manager

Unlike Ovid/Ebsco databases and PubMed, The Cochrane Library does not automatically keep your search lines in the search history. You must manually add each search line by choosing the Add to Search Manager link.

Go to the Search Manager tab to view all your saved search lines. Log into your account to save the complete search history and name your search.

Cochrane Library: advanced search tips

  • Use NEXT to search for heart attack or heart attacks, but not attacking the heart. For example: heart NEXT attack*. This operator assumes the terms are in the direction keyed. Don't use numbers with NEXT, such as NEXT/2.
  • Use NEAR to search for words appearing in either direction, with a number to denote the maximum number of words between the terms. For example: heart NEAR/2 attack* will find heart attack, heart attacks, attacking the child’s heart, heart that is attacked.
  • Truncate search terms using an asterisk*. For example: heart attack* will find papers on heart attack, heart attacks, attacking heart. The root word must be at least 3 characters.
  • Enclose terms in quotation marks to search for an exact phrase. For example: "heart attack" will find only that exact phrase. Do not enclose an asterisk in a phrase, for example "heart attack*".

Limit to peer reviewed journals in EBSCO databases

In Ebsco's CINAHL and ERIC databases you can limit your results to peer reviewed journals. Use the Edit link in your search history and select Peer Reviewed. The peer reviewed option is not available in Medline.

Proximity searching in EBSCO databases

Use W1 to find words next to each other in EBSCO, for example: heart W1 attack will find the phrase "heart attack". W1 implies the search is directional; the word heart comes before the word attack.

Use N with a number, for example N3, to increase the sensitivity of your search. The N is non-directional, so a search for heart N3 attack will find both terms in any direction with up to three words in between, for example this would find the phrases: attack on heart, heart drug could reduce attack.

This tip can only be applied to keyword searching.

Wildcards and truncation in EBSCO databases


  • Represented by a question mark ? or pound sign #.
  • Use question mark ? to replace a character, for example: wom?n will find woman or women.
  • Use pound sign # where an alternate spelling may contain an extra character, for example, labo#r will find labour or labor.
  • Truncation: represented by an asterisk *
  • Usage: computer* will find computer, computers, computerised or computerized.

Special notes

  • Wildcard and truncation cannot be combined in a term. For example, searching for p#ediatric* is the same as a search for p*.
  • Can only be applied to keyword searching.

Ovid search filters

Search filters will limit your results to a specific population group, study type or setting.

These search filters are available for Ovid databases:

  • Diagnosis
  • Etiology
  • Prognosis
  • Therapy
  • Meta-analysis
  • Cochrane (RCT)
  • Age filter for 0-24 years old
  • Developing countries
  • WHO articles
  • Premature/preterm
  • Systematic reviews
  • Refugee
  • Epidemiologic
  • Animals-only

Access the search filters by logging into your Ovid Personal Account, then go to My Workspace/My Searches & Alerts/Expert Searches.

Filters are database specific, so be sure to select the right filter for the database you are using.

Multiple database searching and duplicate records in EndNote

We recommend that you use multiple databases, one at a time, for a comprehensive search, and export all relevant records to EndNote. However, this will usually result in duplicate records.

Use the Find Duplicates function in EndNote to find most of the duplicates and delete, then manually remove the remaining.

Searching for Greek letters in Ovid

Greek letters are transliterated and indexed as their text equivalents. For example, the Greek letter Α appears in records as <alpha>, with angle brackets enclosed around the word alpha. To search the Greek letter Α, use quotation marks, for example "<alpha>".

Quickly switch to another database

In Ovid databases

When you have searched in an Ovid database such as Medline or Embase, you can use the Change link to select a different Ovid database and start another search. Be sure to select OK, do not select Run Search.

In Ebsco databases

When you have completed your search in Medline, for example, use the Choose Databases link to select a different database, such as CINAHL. Be sure to deselect Medline first, then choose OK.

Customise your NCBI PubMed account

You can configure your My NCBI to show Free Full Text and RCH Full Text in PubMed searches by customising your preference settings. When logged in, your own preferences will override any institutional settings.

See Fact Sheet no.14: PubMed: search, save, and manage results for detailed instructions.

Ovid session time out message

You may be confronted with a "time out" message in Ovid databases

This means you were idle for too long, or you took too long browsing results without interacting with the interface. Tests have proven inconclusive, but we typically expect time outs to occur after about 20 minutes.

To reconnect, don't fill in the login fields, just hit the Login button if you are on site at RCH, or use the OpenAthens Login link if you are off site.

This is a timely reminder to save your search frequently. All work will typically be lost after the last save point.

Search Tip: using My Projects or Custom Folders effectively

Add your search results into My Projects in Ovid databases, or Custom Folders in EbscoHOST databases, for follow-up later.

In order to export records from the Project/Folder into EndNote, you must create individual Projects/Folders for each database.

For example, Ovid Medline citations must be placed into a separate Project from Ovid Embase citations. Similarly, citations from EbscoHOST Cinahl must be placed into a separate Folder from EbscoHOST ERIC citations. If all citations are bundled into a single Project/Folder, they cannot be exported into EndNote.

Using AND, OR in Google or Google Scholar

You don't need to use AND to combine search terms in Google or Google Scholar; it's the default operator and will be ignored.

However, the OR operator is accepted, but it must be in capitals. Alternatively you can use the pipe | to replace the OR.

For example: Dementia methylphenidate|ritalin will give the same results as Dementia methylphenidate OR ritalin.

Both will search for dementia with methylphenidate as well as dementia with ritalin.

Google/Google Scholar and parentheses

Don't use parentheses in Google or Google Scholar searching: parentheses are ignored. A search for Dementia (methylphenidate OR ritalin) will find the same results as Dementia methylphenidate OR ritalin.

Google/Google Scholar and the asterisk*

You can't use the asterisk* for truncation, for example neonat*, but you can use it to replace a single unknown term in a search query or phrase. You can even use more than one, but when they are applied in a row there must be a space between each one. For example:

"The * * that you absolutely have to know, is the * of the *"

This search string would find the quote by Albert Einstein: "The only thing that you absolutely have to know, is the location of the library".

Google/Google Scholar and excluding or including search terms

To exclude a term from your search results, use the minus(-) sign. Do not use NOT. For example:

dementia methylphenidate OR ritalin -sleep -appetite

This will exclude sleep and appetite.

To include a term in your search, just enter the term. Do not use the plus(+) sign. For example:

dementia methylphenidate OR ritalin apathy

This will find dementia with either methylphenidate or ritalin, as well as apathy.

Use a command to run your saved search in Ovid databases

You can use an easy shortcut command to run your saved search right from the Search box in any Ovid database.

You must be logged into your personal account first for this to work.

..e your search name

So, if the name of your saved search is Asthma-medline, your command will be:

..e Asthma-medline

Note the double dots and space before the search name. The search name must be exact and is case sensitive.

Truncation and wildcards in databases

The most common truncation symbol is an asterisk (*) but this can differ between database; always check the Help information in each database.

In PubMed, Ovid and EbscoHost databases, the asterisk (*) is used to find all different word endings. For example: emergency department* will retrieve emergency department or emergency departments; and arter* will find artery, arteries or arterial.

Truncation and wildcards should only be used for keywords, never for thesaurus terms.

Wildcards for Ovid databases

  • Use # to replace exactly 1 character, .e.g. wom#n will find woman or women
  • Use ? to find 0 or 1 character, e.g. labo?r will retrieve labor or labour

Wildcards for EbscoHost databases

  • Use # to find 0 or 1 character, e.g. labo#r will retrieve labor or labour
  • Use ? to replace exactly 1 character, .e.g. wom?n will find woman or women

Use the hyphen for keyword phrase searching

Keyword searching is necessary when there are no appropriate thesaurus terms available, when the database does not support thesaurus searching, or if the search needs to be very sensitive.

Different databases have different rules when it comes to keyword searching

Ovid databases do not support phrase searching using “quotation marks”, while some databases that do support the use of quotation marks will not allow truncation symbols within the phrase.

To save time creating a keyword search string that is acceptable across multiple databases, use the hyphen instead of quotation marks to join your terms. As a general rule you can apply a truncation symbol (typically the asterisk* but not always) for the last word only.

For example: heart-transplant* will find the following phrases: heart transplant, heart transplants, heart transplantation, heart transplantations.

Quickly export a large number of records from Ovid databases into EndNote

The maximum number of citations you can export from Ovid Medline and Embase is 1000.

In APA PsycInfo, some citations can have thousands of references but only 200 can be exported at a time.

This can sometimes be a lengthy process.

You can avoid exporting in batches of 200, or to speed up the process overall, by choosing Citation, Abstract instead of Complete Reference in the Export Citation options.

Use Contexts in Ovid Medline to check for narrower terms

When a MeSH term appears to have no narrower term(s), use Contexts to see if there are narrower terms under a different branch.

For example, the MeSH tree for Ambulances falls under the Motor Vehicles branch and has no visible narrower term(s).

Select Contexts from the top of the tree to view other branch(es) for Ambulances.

This shows that Ambulances also falls under the branch Transportation of Patients and has a narrower term Air Ambulances.

Select Ambulances and Explode to include Air Ambulances in your search.

Exclude animal-only studies in Ovid databases

To limit to human studies, do not use the Humans limit. Instead, exclude all animal-only studies from your search

For example: a sample search looks for studies on drug therapy in cancer …

Search line #1:


Identify all animal-only studies …

Search line #2:

Exp Animals/ not human*.sh. (for Ovid Medline)
Exp Animal/ not human*.sh. (for Ovid Embase)
(animal not human).po. (for Ovid APA PsycInfo)

Remove the animal-only studies from your search results …

Search line #3:

1 NOT 2

Results in Search line #3 will retain Humans only, joint Humans and Animals, and any studies that haven't been assigned as either Humans or Animals.

The terms in Search line #2 are saved as filters. See the tip Ovid search filters for how to apply the filter to your search.

Go to My Searches & Alerts to view your saved Ovid search

After logging into your personal Ovid database account you may not be able to see your saved search. Don't panic! In your My Workspace area make sure that you are in My Searches & Alerts, not My Projects.

Ebsco databases: force your search history to display in ascending order

By default, the search history in Ebsco displays in descending order. To reverse the order, choose the Search ID# above your last search line in the search history box:

Merging personal accounts in Ebsco databases

If you have two Ebsco personal accounts, you can merge them into one single account. If you have more than two accounts, repeat the process until all accounts are merged into one.

All saved searches, alerts, custom folders etc. will be stored in the one account.

Choose wisely

If the accounts being merged are from different institutions, only content available in the target institution will be merged.

This is because available content will differ between institutions, so only the content that is available from the institution through which the target account was created will be merged.

 Learn more.

Search the thesaurus when possible

Always check if the database you are searching supports a thesaurus.

Thesaurus searching is preferred because it searches the concept, that is to say it locates relevant material about the search term(s), whereas keyword searching only looks to match the actual words used in the search.

If thesaurus searching is available, there is typically a 'map to' thesaurus/subject heading/descriptor, and most likely found in Advanced Search options.

For more information about differences between thesaurus versus keyword searching, see search tip: Understanding the difference between keyword searching and thesaurus searching.

Ask a Librarian

See literature search support at the Library website for help with searching.

If you've already started searching in an Ovid or Ebsco database and encounter difficulties, use the Ask a Librarian feature within the search interface.

You will receive a response within 24 hours (Monday-Friday). Your current search history will be included with your enquiry.

Always search more than one database

To do a comprehensive search, always perform your search in more than one database.

Each database indexes different journals, so start with the most relevant database for your discipline, then do an equivalent search in the next relevant database.

See How to choose the right database for help.

Type of review determines how you search

Here we describe the common types of reviews and how comprehensive your search must be

Literature/Integrative/Narrative/Historical review

Reviews existing literature on a broad question. Your search does not have to be comprehensive.

Scoping/Mapping review

Reviews existing literature to identify research gaps, and could lead to a systematic review. Your search must be comprehensive but will have time and scope constraints.

Rapid review

Answers a specific question usually for a policy/practice. Searching is comprehensive but has time constraints.

Umbrella review

Also known as systematic review of systematic reviews, review of reviews, synthesis of reviews, review of meta-analyses, meta-review and systematic meta-review. This type of review aims to bring together evidence from high-quality sources such as systematic reviews or meta-analyses into one overview to make it easy to compare and contrast them. Your search must be comprehensive.

Systematized review

Methodology is similar to a systematic review but not quite as stringent and is typically conducted as a postgraduate assignment. Your search may or may not be comprehensive.

Systematic review

This type of review answers a specific question. It requires a comprehensive and exhaustive search strategy, and must have a defined inclusion/exclusion criteria determined at the protocol stage.

For more information see:

Search across multiple databases

While we recommend that you search across multiple databases so your search becomes more comprehensive, you must always adapt your search terms and syntax to suit each database and platform:

  • Always search one database at a time. Do not run the same search strategy across multiple databases at the same time.
  • Thesaurus terms get updated regularly so always check that the thesaurus terms are up-to-date before you rerun a saved search.
  • Each database thesaurus has its own unique terms; they may be the same but you should never assume that. Always update the thesaurus terms for each database.
  • Proximity operators can be different for each platform. For example, : ADJ (Ovid); N (Ebsco); NEAR (Cochrane Library/Proquest) and some databases like PubMed do not support any proximity searching. For search terms that consist of keywords only, always check the syntax before using it in different databases.

Save your database searches

Create an account in Ovid, EbscoHost, ProQuest, PubMed, Cochrane Library, or other database, to save your search history to edit or run later. You can also create regular alerts.

Refer to our Fact sheets for more information.

Cochrane Library: View saved searches

You must be in the Search Manager tab when selecting View saved searches to see all your saved searches.

While the View saved searches link is also available in the Search or Medical terms (MeSH) tabs, it will not actually display your saved searches there.

Select Load underneath the saved search to run your saved search.