Is there a way to use MySQL fulltext to search related tables? - mysql

Question

I have a table called persons which contains data about, well, people. It also contains foreign keys to another table. I'd like to make a fulltext index that is able to search the related tables for full text.
Here is some sample data: (see http://sqlfiddle.com/#!9/036fc5/2)
CREATE TABLE IF NOT EXISTS `states` (
`id` char(2) NOT NULL,
`name` varchar(45) NOT NULL,
PRIMARY KEY (`id`)
);
INSERT INTO `states` (`id`, `name`) VALUES
('NY', 'New York'),
('NJ', 'New Jersey'),
('CT', 'Connecticut'),
('PA', 'Pennsylvania');
CREATE TABLE IF NOT EXISTS `persons` (
`id` int auto_increment NOT NULL,
`first_name` varchar(45) NOT NULL,
`last_name` varchar(45) NOT NULL,
`state_id` char(2) not null,
PRIMARY KEY (`id`),
FULLTEXT (first_name, last_name, state_id)
);
INSERT INTO `persons` (`first_name`, `last_name`, `state_id`) VALUES
('Arnold', 'Asher', 'NY'),
('Bert', 'Bertold', 'NJ'),
('Charlie', 'Chan', 'NJ'),
('Darrin', 'Darcy', 'CT');
So, I'd like to be able to search for persons from "Jersey", such as:
SELECT * FROM persons WHERE MATCH(first_name, last_name, state_id) AGAINST('Jersey');
But, of course, the text "Jersey" exists only in the states table and not in the persons table. Does it make sense to make a materialized/generated index? Is there a simpler way?

Answer 1

You need to put a separate full-text index on the states table, and join with that.
CREATE TABLE IF NOT EXISTS `states` (
`id` char(2) NOT NULL,
`name` varchar(45) NOT NULL,
PRIMARY KEY (`id`),
FULLTEXT (name)
);
CREATE TABLE IF NOT EXISTS `persons` (
`id` int auto_increment NOT NULL,
`first_name` varchar(45) NOT NULL,
`last_name` varchar(45) NOT NULL,
`state_id` char(2) not null,
PRIMARY KEY (`id`),
FULLTEXT (first_name, last_name);
SELECT p.*
FROM persons p
JOIN states s ON s.id = p.state_id
WHERE MATCH(s.name) AGAINST ('Jersey')
UNION
SELECT *
FROM persons
WHERE MATCH(first_name, last_name) AGAINST ('Jersey')

Answer 2

In MySQL, no type of index spans multiple tables. Not fulltext indexes, not spatial indexes, not btree indexes, not hash indexes.
Every type of index you can define belongs to exactly one table, and can index only the values in that table.