Fuzzy

Use the fuzzy operator to expand queries to include words that are spelled similarly to the specified term. This type of expansion is helpful for finding more accurate results when there are frequent misspellings in your document set.

The new fuzzy syntax enables you to rank the result set so that documents that contain words with high similarity to the query word are scored higher than documents with lower similarity. You can also limit the number of expanded terms.

Unlike stem expansion, the number of words generated by a fuzzy expansion depends on what is in the index. Results can vary significantly according to the contents of the index.

Supported Languages

Oracle Text supports fuzzy definitions for English, German, Italian, Dutch, Spanish, and OCR.

Stopwords

If the fuzzy expansion returns a stopword, the stopword is not included in the query or highlighted by CTX_DOC.HIGHLIGHT or CTX_DOC.MARKUP.

Base-Letter Conversion

If base-letter conversion is enabled for a text column and the query expression contains a fuzzy operator, Oracle operates on the base-letter form of the query.

Syntax

fuzzy(term, score, numresults, weight)

Parameter	Description
term	Specify the word on which to perform the fuzzy expansion. Oracle expands term to include words only in the index.
score	Specify a similarity score. Terms in the expansion that score below this number are discarded. Use a number between 1 and 80. The default is 60.
numresults	Specify the maximum number of terms to use in the expansion of term. Use a number between 1 and 5000. The default is 100.
weight	Specify WEIGHT or W for the results to be weighted according to their similarity scores. Specify NOWEIGHT or N for no weighting of results.

Examples

Consider the CONTAINS query:

...CONTAINS(TEXT, 'fuzzy(government, 70, 6, weight)', 1) > 0;

This query expands to the first six fuzzy variations of government in the index that have a similarity score over 70.

In addition, documents in the result set are weighted according to their similarity to government. Documents containing words most similar to government receive the highest score.

You can skip unnecessary parameters using the appropriate number of commas. For example:

'fuzzy(government,,,weight)'

Backward Compatibility Syntax

The old fuzzy syntax from previous releases is still supported. This syntax is as follows:

Parameter	Description
?term	Expands term to include all terms with similar spellings as the specified term.