Question

Method #1 (fulltext):

CREATE TABLE `addresses` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `mail` text NOT NULL,
  PRIMARY KEY  (`id`),
  FULLTEXT KEY `mail` (`mail`)
);

find out exists with searching:

SELECT * FROM addresses WHERE MATCH(email) AGAINST('"[e-mail]"' IN BOOLEAN MODE)

or method #2 (unique varchar):

CREATE TABLE `addresses` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `mail` varchar(100) NOT NULL,
  PRIMARY KEY  (`id`),
  UNIQUE KEY `mail` (`mail`)
);

find out exists with insert:

INSERT INTO `addresses` (`id`, `mail`) VALUES (NULL ,  '[e-mail]');

if fail then exists:

#1062 - Duplicate entry '[e-mail]' for key 2 

which method is better for find out exists mail addresses in thousands of rows?

Answer 1

Method 3 (with the unique varchar) is better:

SELECT * FROM addresses WHERE email = '[e-mail]'

FullText search for a exact match isn’t a great idea and using an insert to test if something exists is just wrong (although correct if you’re planning to insert it regardless).

Note that the unique constraint can be case insensitive depending on the encoding. If you use utf-8-bin it will be base sensitive.