Add relevant search results, expand your search to all fields in a database, and run “fuzzy” searches in MySQL.
TL;DR: The bigger and more complicated the database, the more talented its search capabilities need to be. These three techniques let you broaden the results returned by MySQL searches: one via automatic relevance feedback, another by searching all fields in all tables of the database, and a third by finding approximate matches to your search term.
A database doesn’t do users much good if they can’t find the data they’re searching for. The larger and more complex the database elements, the more sophisticated your searches have to be to return the information you need.
In MySQL, full-text indexes apply to CHAR, VARCHAR, or TEXT columns in InnoDB and MyISAM tables. As the MySQL Reference Manual explains, full-text searchers are done using the MATCH() … AGAINST syntax: the former accepts a comma-separated list identifying the columns to be searched; and the latter accepts a string to search for, and optionally a modifier indicating the type of search to be conducted.
The three types of full-text searches are natural language, boolean, and query expansion, which broadens the results of a natural-language search based on automatic relevance feedback (also called blind query expansion). A MySQL Tutorial steps through the process of crafting and applying a query expansion search.
When you add WITH QUERY EXPANSION to the AGAINST() function, the MySQL search engine first finds all rows matching the search query, then it checks those rows for the relevant words, and finally it searches again based on the relevant words rather than the user’s original keywords. The tutorial uses the example of a search of a car database with and without query expansion.
Multiple ways to search all tables in MySQL
When a Stack Overflow poster asked how to search all fields in all tables of a MySQL database, several different solutions were offered. The simplest is a SQLDump and then search the database as a file. To make the result easier to read, use –extended-insert=FALSE flag for mysqldump.
Another option is to use the search feature in phpMyAdmin: select the database, choose Search, enter your search term, and select the tables to be searched. A third solution is the following function:
Use SoundEx to include approximations in search results
Approximate string matching is an algorithmic trick upon which empires have been built. However, the fuzzy searching techniques that are common in Web search engines are lacking in MySQL, at least in terms of a direct equivalent search function. In a March 9, 2015, post, Database Journal’s Rob Gravelle describes how to use the SoundEx phonetic algorithm to perform fuzzy searches in MySQL.
SoundEx reduces text to the sound when spoken. This makes it easy to spot misspellings, which are likely to have the same SoundEx string as the correct spelling. The three arguments the function takes are the needle (the search target), haystack (the text to be searched), and splitChar (usually a space).
Gravelle devises a function he names soundex_match_all that extends SoundEx to search for strings of words.
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