Common Boolean Search Mistakes (And How to Fix Them)
A search string that returns zero results, or hundreds of irrelevant ones, is almost always a syntax problem rather than a real absence of matching candidates. These six mistakes account for most of them.
Missing parentheses around an OR group
Placing an OR group next to AND without brackets changes what the string actually matches, because AND is usually evaluated before OR. "nurse" AND ICU OR "intensive care" can be read as matching anything containing "intensive care" alone, with no nurse requirement at all.
Fix: always wrap an OR group in parentheses: "nurse" AND (ICU OR "intensive care").
Typing operators in lower case
Most platforms, including LinkedIn and Google, only recognise AND, OR and NOT as operators when capitalised. Typed in lower case, "and" or "or" is usually treated as an ordinary search word instead of an instruction — which quietly changes the results without any error message.
Fix: always capitalise AND, OR and NOT in full.
Unclosed quotation marks or brackets
A single missing closing quote or parenthesis can cause a search engine to misinterpret the entire remainder of the string, often returning an unrelated or empty result set with no clear indication of what went wrong.
Fix: count opening and closing marks before running a long string — most editors will highlight a mismatched pair if you paste the string into a plain text field first.
Over-excluding with too many NOT terms
Each NOT removes any result containing that word anywhere, including in contexts unrelated to the reason you added it. Excluding "graduate" to filter out junior candidates, for example, also removes experienced candidates who happen to mention a graduate scheme they completed years earlier.
Fix: use NOT for genuinely unambiguous terms only, and review whether a filter (such as LinkedIn's seniority filter) would achieve the same goal more precisely.
Searching an exact job title with no OR alternatives
Job titles vary significantly between companies for the same role. A string built around one exact title in quotes, with no OR-linked alternatives, systematically misses candidates whose employer used a different label.
Fix: brainstorm 2–4 real title variants before writing the string, and link them with OR inside parentheses.
Pasting a boolean string into the wrong field
On LinkedIn specifically, boolean syntax only works in the main free-text search bar and Recruiter's keyword field — not inside structured filters like current company or school, where it is read as literal text instead of logic (see our LinkedIn guide for the full breakdown).
Fix: keep boolean-structured terms in the main keyword search bar, and use LinkedIn's dedicated filters for anything they already handle, like location or industry.
Still stuck?
Revisit the fundamentals in Boolean Operators Explained, or check platform-specific quirks in LinkedIn Boolean Search and CV & X-Ray Sourcing Strings. If your question isn't answered there, see our full FAQ page or get in touch.