How to perform search on MySQL table for a website

How do I perform a search similar to that of Wikipedia on a MySQL table (or several tables at a time) without crawling the d开发者_如何学JAVAatabase first? (Search on wikipedia used to show you the relevancy in percentage).

What I'm looking for here is how to determine relevancy of the results and sort them accordingly, especially in case where you pull data from several tables at a time.

What do you use for search function on your websites?

You can use MySQL's full-text search functionality. You need to have a FULLTEXT index on the fields to be searched. For natural language searches, it returns a relevance value which is "a similarity measure between the search string and the text in that row."

If you are searching multiple tables, the relevance value should be comparable across sets of results; you could do a UNION of individual fulltext queries on each of the tables, then sort the results of the union based on the relevance value.