Search for Words Close to Another Word with NEAR

Artikel
02/28/2023

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

You can use the proximity term NEAR in a CONTAINS predicate or CONTAINSTABLE function to search for words or phrases near one another.

Overview of NEAR

NEAR has the following features:

You can specify the maximum number of non-search terms that separate the first and last search terms.
You can search for words or phrases in any order, or you can search for words and phrases in a specific order.
You can specify the maximum number of non-search terms, or maximum distance, that separates the first and last search terms in order to constitute a match.
If you specify the maximum number of terms, you can also specify that matches must contain the search terms in the specified order.

To qualify as a match, a string of text must:

Start with one of the specified search terms and end with the one of the other specified search terms.
Contain all of the specified search terms.
The number of non-search terms, including stopwords, that occur between the first and last search terms must be less than or equal to the maximum distance, if the maximum distance is specified.

Syntax of NEAR

The basic syntax of NEAR is:

 NEAR (  
  
 {  
  
 *search_term* [ ,...*n* ]  
  
 |  
  
 (*search_term* [ ,...*n* ] ) [, <maximum_distance> [, <match_order> ] ]  
  
 }  
  
 )

For more info about the syntax, see CONTAINS (Transact-SQL).

Examples

Example 1

For example, you could search for 'John' within two terms of 'Smith', as follows:

... CONTAINS(column_name, 'NEAR((John, Smith), 2)')

Some examples of strings that match are "John Jacob Smith" and "Smith, John". The string "John Jones knows Fred Smith" contains three intervening non-search terms, so it is not a match.

To require that the terms be found in the specified order, you would change the example proximity term to NEAR((John, Smith),2, TRUE). This searches for "John" within two terms of "Smith" but only when "John" precedes "Smith". In a language that reads from left to right, such as English, an example of a string that matches is "John Jacob Smith".

Note that for a language that reads from right to left, such as Arabic or Hebrew, the Full-Text Engine applies the specified terms in reverse order. Also, Object Explorer in SQL Server Management Studio automatically reverses the display order of words specified in right-to-left languages.

Example 2

The following example searches the Production.Document table of the AdventureWorks sample database for all document summaries that contain the word "reflector" in the same document as the word "bracket".

SELECT DocumentNode, Title, DocumentSummary  
FROM Production.Document AS DocTable   
INNER JOIN CONTAINSTABLE(Production.Document, Document,  
  'NEAR(bracket, reflector)' ) AS KEY_TBL  
  ON DocTable.DocumentNode = KEY_TBL.[KEY]  
WHERE KEY_TBL.RANK > 50  
ORDER BY KEY_TBL.RANK DESC;  
GO

How maximum distance is measured

A specific maximum distance, such as 10 or 25, determines how many non-search terms, including stopwords, can occur between the first and last search terms in a given string. For example, NEAR((dogs, cats, "hunting mice"), 3) would return the following row, in which the total number of non-search terms is three ("enjoy", "but", and "avoid"):

"Cats enjoy hunting mice``, but avoid dogs``."

The same proximity term would not return the following row, because the maximum distance is exceeded by the four non-search terms ("enjoy", "but", "usually", and "avoid"):

"Cats enjoy hunting mice``, but usually avoid dogs``."

Combine NEAR with other terms

You can combine NEAR with some other terms. You can use AND (&), OR (|), or AND NOT (&!) to combine a custom proximity term with another custom proximity term, a simple term, or a prefix term. For example:

CONTAINS('NEAR((term1, term2),5) AND term3')
CONTAINS('NEAR((term1, term2),5) OR term3')
CONTAINS('NEAR((term1, term2),5) AND NOT term3')
CONTAINS('NEAR((term1, term2),5) AND NEAR((term3, term4),2)')
CONTAINS('NEAR((term1, term2),5) OR NEAR((term3, term4),2, TRUE)')

For example,

CONTAINS(column_name, 'NEAR((term1, term2), 5, TRUE) AND term3')

You can't combine NEAR with a generation term (ISABOUT ...) or a weighted term (FORMSOF ...).

Dela via

Search for Words Close to Another Word with NEAR

Overview of NEAR

Syntax of NEAR

Examples

Example 1

Example 2

How maximum distance is measured

Combine NEAR with other terms

More info about proximity searches

See Also

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