MySQL Query Expansion Fulltext Search

The MySQL can perform full-text searches using the MATCH ... AGAINST clause in combination with the BOOLEAN MODE. Full-text search allows you to search for words and phrases in text columns efficiently. Here’s how you can use it:

Assuming you have a table named articles with a text column content, and you want to search for articles containing specific words or phrases:

1. Create a Full-Text Index: Before you can perform full-text searches, you need to create a full-text index on the column you want to search. You can do this when creating the table or alter an existing table. CREATE TABLE articles ( id INT AUTO_INCREMENT PRIMARY KEY, title VARCHAR(255), content TEXT, FULLTEXT(content) );
2. Perform a Full-Text Search:
   • To perform a full-text search, you use the MATCH ... AGAINST clause in your SQL query.
   • You can use the + and - operators to include or exclude specific words.
   • You can use double quotes " to search for an exact phrase.
   For example, to search for articles that contain the words “database” and “query” and exclude any articles with the word “NoSQL”: SELECT * FROM articles WHERE MATCH(content) AGAINST('+database +query -NoSQL' IN BOOLEAN MODE);
3. Sorting by Relevance: You can also sort the results by relevance using the MATCH ... AGAINST clause in the ORDER BY clause: SELECT *, MATCH(content) AGAINST('+database +query -NoSQL' IN BOOLEAN MODE) AS relevance FROM articles WHERE MATCH(content) AGAINST('+database +query -NoSQL' IN BOOLEAN MODE) ORDER BY relevance DESC;
4. Word Length Limit: By default, MySQL’s full-text search ignores words that are too short (less than 4 characters) and words that are very common (stopwords). You can adjust these settings in the MySQL configuration.
5. Boolean Mode: The IN BOOLEAN MODE option allows you to use operators like +, -, *, etc., for more complex queries. In non-boolean mode, you can simply use MATCH ... AGAINST('your_query').
6. Thesaurus Support: You can also use a thesaurus file to extend the search capabilities. For example, you can specify synonyms for specific words.

Keep in mind that full-text search in MySQL may not be as feature-rich as specialized search engines like Elasticsearch, so consider your requirements and scale when implementing full-text search in your applications.