Minimum Should Match (find at least n terms from a list) allows you to conduct a more controlled search on related or co-occurring topics by specifying the number of search terms or phrases in the query that should occur within the records returned.
Minimum Should Match allows you to specify the number of different matched terms or phrases required to occur in a document in order to be returned in the results. Setting Minimum Should Match to 1 is the same as conducting an ordinary OR search. Note: If the AND boolean operator is selected (this is the case by default), the minumim match syntax will override this and use OR.
To execute a Minimum Should Match query, use the syntax in the example below:
(“lung cancer” COPD lymphoma)~2 or (“lung cancer” COPD lymphoma)@2
The query must be structured such that the terms are within parentheses and the number of terms you wish to match follows a tilde (~) or an at (@) symbol with no spaces. If certain terms or phrases are required to appear in the records returned, include a plus sign (+) directly in front of the required search term(s) or phrase(s). For example:
(“lung cancer” +COPD lymphoma)~2
In the above example, COPD will appear in all records returned and at least 2 of the remaining search terms and phrases will appear in the records returned.
When a plus sign (+) is placed in front of a search term or phrase it is not included in the execution of the Minimum Should Match query because Minimum Should Match is only executed on optional terms and phrases.
Alternatively, to exclude a search term or phrase from appearing in the documents returned, include a minus sign (-) directly in front of the search term or phrase. For example:
(“lung cancer” -COPD lymphoma)~2
In the example above, records containing COPD will be excluded and at least 2 of the remaining search terms or phrases will appear in the records returned.
The sub-clauses of a Boolean query can themselves be complex queries. In the example below, Minimum Should Match selects documents that match at least two of the provided three sub-clauses. The three sub-clauses are (yellow OR blue), crab, fish:
- ((yellow OR blue) crab fish)@2
- ((yellow OR blue) crab fish)~2
Minimum Should Match is most useful when querying a large number of search terms or phrases where only some of the terms are necessary to be considered relevant to the search but OR is too lenient.