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Using wildcards in MySQL fulltext searches

Posted on 2008-10-02
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Last Modified: 2012-05-05
I'm using a MySQL database, and I have a table containing a text field. I was using a query to return all rows containing a string within the text field -

... WHERE desc like '%MSDN%'

But this is was too slow on a large table. I speeded this up by using a fulltext index on the 'desc' column in my table.
However, the equivalent fulltext search clause

... MATCH desc AGAINST ('MSDN')

returns rows matching

...w/MSDN Prem...

but not

...w/MSDNPrem...

I've tried modifying my fulltext search with wildcards i.e.

... MATCH desc AGAINST ('*MSDN*')

but this didn't work, I still didn't get the complete set of matches I expected. Does anyone know what the equivalent fulltext search pattern is, to return exactly the same resultset as my original query?
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Question by:smartstream-stp
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Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 22622620
what about:
... MATCH desc AGAINST ('MSDN*')

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Author Comment

by:smartstream-stp
ID: 22622740
Unfortunately that doesn't work. 'MSDN*' does not return rows containing '...w/MSDNPrem...'
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LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 22622769
first you cannot use *something in FT...

so, I am not sure, but maybe / is not a word breaker....
http://dev.mysql.com/doc/refman/5.0/en/fulltext-fine-tuning.html

#If you want to change the set of characters that are considered word characters, you can do so in two ways. Suppose that you want to treat the hyphen character ('-') as a word character. Use either of these methods:
 
    *    Modify the MySQL source: In myisam/ftdefs.h, see the true_word_char() and misc_word_char() macros. Add '-' to one of those macros and recompile MySQL.
 
    *    Modify a character set file: This requires no recompilation. The true_word_char() macro uses a character type table to distinguish letters and numbers from other characters. . You can edit the <ctype><map> contents in one of the character set XML files to specify that '-' is a letter. Then use the given character set for your FULLTEXT indexes.
 
After making the modification, you must rebuild the indexes for each table that contains any FULLTEXT indexes.

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Accepted Solution

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jericotolentino earned 1500 total points
ID: 22622902
Try if MySQL boolean search works for you:

SELECT *,MATCH(desc) AGAINST ('*MSDN*' IN BOOLEAN MODE) AS score FROM search WHERE MATCH(desc) AGAINST ('*MSDN*' IN BOOLEAN MODE);

It requires that you're using MyISAM and the indexes you're searching are of type varchar or text.

More info is available here:
http://dev.mysql.com/doc/refman/5.0/en/fulltext-search.html
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Author Comment

by:smartstream-stp
ID: 22622945
If '/' isn't a word breaker, then how is 'w/MSDN Prem' matched, but not 'w/MSDNPrem' ?

I don't think fulltext indexing is going to be 100% reliable for me, as it relies on the text field being split into words. In my case I can't guarantee this. I don't think there is any direct equivalent for 'WHERE desc LIKE '%MSDN%' i.e. matching an aribitrary string within a text field.

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Author Comment

by:smartstream-stp
ID: 22622997
jericotolentino's suggestion worked much better, but didn't match a field value of

VStudio Team Ed Sft Test AllLngLic/SAOLVNL1YRAcqY1wMSDNPrmAdPrdPrtnrOnly
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