The keywords are the core of your search. Your search will be entirely reliant on these for records without headings (e.g. very new 'in process' records, and for records in databases without consistently applied headings (e.g. Scopus)). Subject headings are a valuable bonus to help you find material. Use the best subject headings available if the database provides a thesaurus, in addition to the keywords.

Always check the thesaurus for the database you are searching. You cannot use all of the MEDLINE headings ('MeSH') in Embase, for example; the Embase thesaurus ('Emtree') has many different and additional headings.

Databases have thesauri that reflect their disciplinary focus. For example, PsycInfo will have many more headings reflecting psychological concepts than you will find in MEDLINE.

See the Subject Headings page of this Guide for more.

For each database with a thesaurus, locate and include all appropriate headings. To locate these, you can:

• search directly in the thesaurus for the terms in your keyword lines, and for headings you found in other databases
• search for the titles of test/sample papers and look at the headings in the records for these
• browse the database thesaurus for broader, narrower and related terms

When you 'explode' a heading, it means (in most databases) that your search will locate all of the records that contain that heading, as well as all those that contain headings that fall below that heading in the hierarchy of terms in the thesaurus.

Some databases default to exploding headings, while for others you have to make a deliberate choice. See the Subject headings page in this Guide, Using subject headings box, Explode tab for more.

If your search has exp or MAINSUBJECT.EXACT.EXPLODE or MH "Heading+" in it, for example - then you are 'exploding' headings!

Explode headings when you are satisfied that all - or most - of the narrower headings are relevant to your search and will retrieve potentially relevant material. Sometimes from a practical perspective you accept some noise e.g. exp Neoplasms/ is often used in MEDLINE to find the 'cancer' concept even if not all narrower headings are relevant. Often it is best to make selections from the narrower terms and include each relevant heading separately.

UniSA Library recommends that you include each subject heading on a separate line for databases available at UniSA via the sophisticated Ovid platform (such as MEDLINE, Embase, Emcare, and PsycInfo). This makes it easier to review the search, see where you have made errors, test the performance of specific headings, and translate the search to other databases.

For databases on other platforms, such as ProQuest and EBSCOhost, it may be easiest to combine multiple headings on one line. See Run your search on other databases for more.

Read over the strategy to spot errors. These are easy to make! We recommend:

• copy and paste subject headings directly from the database thesaurus rather than re-typing these - they need to be exact
• watch for Word auto-correcting terms e.g. adding an e to a term you wanted to truncate e.g. behav* - it may be best to work in another program such as Notepad, or switch off AutoCorrect
• read back over the strategy with fresh eyes after a break, or ask a colleague to take a quick look!
• check spelling in a dictionary if you are not sure

Generally, you will use the connecting term (Boolean operator) 'OR' to combine all of the relevant subject headings and keywords for each search set. This helps to find all of the possible alternative ways that element/concept might appear in records.

You then use the connecting term 'AND' to combine the different search sets and narrow your search to only combinations of one or more terms from each of the search sets.

It's easy to make mistakes with this, especially if your search is long and complex, and if you are making frequent edits.

We recommend:

• use a format where the line numbers are easily viewable - e.g. Notepad, Ovid Search Launcher, Ovid search history emailed to yourself
• if your search is long and complex, rather than using 'Edit' in Ovid work in a separate file (e.g. Notepad), then fix up the line combinations at the end
• in Ovid, you can add notes in square brackets - so you can add explanatory notes as an aid e.g. 10 AND 15 [skin cancer - surveillance]
• use range searching where available e.g. OR/7-15 rather than 7 OR 8 OR 9 OR 10...etc. - see the key search tips handout for details
• combine all lines of a search set with OR on a new line before starting your next search set rather than adding all of your combination lines at the end of your strategy. This adds clarity and makes the strategy easier to read and interpret
• if all else fails...print it out and use colour coding or whatever works best for you to work out the correct sets and combinations!

If you type or paste in your keywords without specifying where these are searched, the database will look for records where these appear in the default 'fields'. Fields are the separately searchable sections of the record where descriptive information about a source is captured (e.g. title, authors, abstract, subject headings)

For many databases, this default set of fields will include the subject headings. For a systematic search you will have carefully chosen which headings you want to search for and this could bring in unwanted records. We recommend limiting your keywords to a specific set of fields. A useful default set is title, abstract and author-supplied keywords, but you can make your own selection of the best combinations for your needs. For more see the keywords page of this Guide, the key search tips handout, and the Help available for specific databases

For some searches, it may be useful to target specific fields, such as author (to find all the works by a highly relevant author), title (for a very general term), or publication type. Field searching is a powerful tool to add to your search toolkit!

Some databases include a search in html full text as part of the default fields, and generally you definitely want to avoid that!

If you have 20,000 results - or 20 - it is likely your search has an issue with one of the following...

• line combinations (use of AND, OR)
• parentheses (round brackets) ('nesting') - for example, do you have the same number of opening and closing brackets?
• database search syntax - e.g. do you need to use double quotation marks around phrases in this database?
• search fields - e.g. are your terms being searched across default fields including full text?
• subject headings - e.g. have you exploded headings leading to large numbers of results; or not exploded when it would help expand your search?
• keywords - e.g. have you included very general terms that can have varied meanings; have you stripped a word stem back too far with truncation; conversely, could you 'open up' your search by using adjacency to accommodate variant phrasing, rather than using exact phrases?
• search sets - e.g. have you combined just a few search sets with broad sets of possible terms, or in areas where a lot has been published; or made too many combinations with 'AND', closing down your search to the point where little is found?