make text column as unique key

mysql sql database unique-key
d-doctor picture d-doctor · Dec 25, 2012 · Viewed 44.4k times · Source

i want to make a table in MySQL server with mediumtext column as UNIQUE KEY

CREATE TABLE `parts` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `name` mediumtext NOT NULL,
      `display_status` int(11) NOT NULL,
       UNIQUE KEY `name` (`name`),
       PRIMARY KEY (`id`)
 ) ENGINE=MyISAM DEFAULT CHARSET=utf8;

but this made an error

    BLOB/TEXT column 'name' used in key specification without a key length

when I change the type of `name` to varchar .. it works!

can you tell if i can to make text column as UNIQUE KEY

Answer

Mari picture Mari · Dec 25, 2012

Basically you can not use Text column as UNIQUE key. Because practically such a big column will not be unique and there might be a chance of more duplicates. So go for hashing method and use that output as a UNIQUE constraint.

Hope this helps you

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