Oracle8i interMedia Text Reference Release 2 (8.1.6) Part Number A77063-01 |
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Query Operators, 9 of 26
Use the MINUS operator to search for documents that contain one query term and you want the presence of a second query term to cause the document to be ranked lower. The MINUS operator is useful for lowering the score of documents that contain unwanted noise terms.
Syntax | Description |
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term1 minus term2 |
Returns documents that contain term1. Calculates score by subtracting occurrences of term2 from occurrences of term1. |
Suppose a query on the term cars always returned high scoring documents about Ford cars. You can lower the scoring of the Ford documents by using the expression:
'cars - Ford'
In essence, this expression returns documents that contain the term cars and possibly Ford; however, the score for a returned document is the number of occurrences of cars minus the number of occurrences of Ford. If a document does not contain any occurrences of the term Ford, no value is subtracted from the score.
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