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MySQL 9.1 Reference Manual  / Functions and Operators  /  Full-Text Search Functions

14.9 Full-Text Search Functions

MATCH (col1,col2,...) AGAINST (expr [search_modifier])

search_modifier:  {       IN NATURAL LANGUAGE MODE     | IN NATURAL LANGUAGE MODE WITH QUERY EXPANSION     | IN BOOLEAN MODE     | WITH QUERY EXPANSION  }

MySQL has support for full-text indexing and searching:

  • A full-text index in MySQL is an index of typeFULLTEXT.

  • Full-text indexes can be used only withInnoDB orMyISAM tables, and can be created only forCHAR,VARCHAR, orTEXT columns.

  • MySQL provides a built-in full-text ngram parser that supports Chinese, Japanese, and Korean (CJK), and an installable MeCab full-text parser plugin for Japanese. Parsing differences are outlined inSection 14.9.8, “ngram Full-Text Parser”, andSection 14.9.9, “MeCab Full-Text Parser Plugin”.

  • AFULLTEXT index definition can be given in theCREATE TABLE statement when a table is created, or added later usingALTER TABLE orCREATE INDEX.

  • For large data sets, it is much faster to load your data into a table that has noFULLTEXT index and then create the index after that, than to load data into a table that has an existingFULLTEXT index.

Full-text searching is performed usingMATCH() AGAINST() syntax.MATCH() takes a comma-separated list that names the columns to be searched.AGAINST takes a string to search for, and an optional modifier that indicates what type of search to perform. The search string must be a string value that is constant during query evaluation. This rules out, for example, a table column because that can differ for each row.

MySQL does not permit the use of a rollup column withMATCH(); more specifically, any query matching all of the criteria listed here is rejected withER_FULLTEXT_WITH_ROLLUP:

  • MATCH() appears in theSELECT list,GROUP BY clause,HAVING clause, orORDER BY clause of a query block.

  • The query block contains aGROUP BY ... WITH ROLLUP clause.

  • The argument of the call to theMATCH() function is one of the grouping columns.

Some examples of such queries are shown here:

# MATCH() in SELECT list...SELECT MATCH (a) AGAINST ('abc') FROM t GROUP BY a WITH ROLLUP;SELECT 1 FROM t GROUP BY a, MATCH (a) AGAINST ('abc') WITH ROLLUP;# ...in HAVING clause...SELECT 1 FROM t GROUP BY a WITH ROLLUP HAVING MATCH (a) AGAINST ('abc');# ...and in ORDER BY clauseSELECT 1 FROM t GROUP BY a WITH ROLLUP ORDER BY MATCH (a) AGAINST ('abc');

The use ofMATCH() with a rollup column in theWHERE clause is permitted.

There are three types of full-text searches:

  • A natural language search interprets the search string as a phrase in natural human language (a phrase in free text). There are no special operators, with the exception of double quote (") characters. The stopword list applies. For more information about stopword lists, seeSection 14.9.4, “Full-Text Stopwords”.

    Full-text searches are natural language searches if theIN NATURAL LANGUAGE MODE modifier is given or if no modifier is given. For more information, seeSection 14.9.1, “Natural Language Full-Text Searches”.

  • A boolean search interprets the search string using the rules of a special query language. The string contains the words to search for. It can also contain operators that specify requirements such that a word must be present or absent in matching rows, or that it should be weighted higher or lower than usual. Certain common words (stopwords) are omitted from the search index and do not match if present in the search string. TheIN BOOLEAN MODE modifier specifies a boolean search. For more information, seeSection 14.9.2, “Boolean Full-Text Searches”.

  • A query expansion search is a modification of a natural language search. The search string is used to perform a natural language search. Then words from the most relevant rows returned by the search are added to the search string and the search is done again. The query returns the rows from the second search. TheIN NATURAL LANGUAGE MODE WITH QUERY EXPANSION orWITH QUERY EXPANSION modifier specifies a query expansion search. For more information, seeSection 14.9.3, “Full-Text Searches with Query Expansion”.

For information aboutFULLTEXT query performance, seeSection 10.3.5, “Column Indexes”.

For more information aboutInnoDBFULLTEXT indexes, seeSection 17.6.2.4, “InnoDB Full-Text Indexes”.

Constraints on full-text searching are listed inSection 14.9.5, “Full-Text Restrictions”.

Themyisam_ftdump utility dumps the contents of aMyISAM full-text index. This may be helpful for debugging full-text queries. SeeSection 6.6.3, “myisam_ftdump — Display Full-Text Index information”.