MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
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 type
FULLTEXT
.
Full-text indexes can be used only with
InnoDB
or
MyISAM
tables, and can be created
only for CHAR
,
VARCHAR
, or
TEXT
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 in Section 12.10.8, “ngram Full-Text Parser”, and Section 12.10.9, “MeCab Full-Text Parser Plugin”.
A FULLTEXT
index definition can be given in
the CREATE TABLE
statement when
a table is created, or added later using
ALTER TABLE
or
CREATE INDEX
.
For large data sets, it is much faster to load your data into
a table that has no FULLTEXT
index and then
create the index after that, than to load data into a table
that has an existing FULLTEXT
index.
Full-text searching is performed using
MATCH() ... 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.
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, see Section 12.10.4, “Full-Text Stopwords”.
Full-text searches are natural language searches if the
IN NATURAL LANGUAGE MODE
modifier is given
or if no modifier is given. For more information, see
Section 12.10.1, “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. The IN BOOLEAN MODE
modifier
specifies a boolean search. For more information, see
Section 12.10.2, “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. The IN NATURAL LANGUAGE MODE WITH
QUERY EXPANSION
or WITH QUERY
EXPANSION
modifier specifies a query expansion
search. For more information, see
Section 12.10.3, “Full-Text Searches with Query Expansion”.
For information about FULLTEXT
query
performance, see Section 8.3.5, “Column Indexes”.
For more information about InnoDB
FULLTEXT
indexes, see
Section 15.6.2.4, “InnoDB FULLTEXT Indexes”.
Constraints on full-text searching are listed in Section 12.10.5, “Full-Text Restrictions”.
The myisam_ftdump utility dumps the contents of
a MyISAM
full-text index. This may be helpful
for debugging full-text queries. See
Section 4.6.3, “myisam_ftdump — Display Full-Text Index information”.