mysql - SQL 错误 : 1170

Question

运行以下代码时出现以下错误...这是怎么回事？

Error Code:1170. BLOB/TEXT column 'message" used in key specification without a key length.

-- MySQL Script generated by MySQL Workbench
-- Sun Jun  4 21:25:42 2017
-- Model: New Model    Version: 1.0
-- MySQL Workbench Forward Engineering

    SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
    SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0;
    SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='TRADITIONAL,ALLOW_INVALID_DATES';

-- -----------------------------------------------------
-- Schema mydb
-- -----------------------------------------------------

-- -----------------------------------------------------
-- Schema mydb
-- -----------------------------------------------------
    CREATE SCHEMA IF NOT EXISTS `mydb` DEFAULT CHARACTER SET utf8 ;
    USE `mydb` ;

-- -----------------------------------------------------
-- Table `mydb`.`users`
-- -----------------------------------------------------
    CREATE TABLE IF NOT EXISTS `mydb`.`users` (
      `id` INT NOT NULL AUTO_INCREMENT,
      `first_name` VARCHAR(255) NOT NULL,
      `last_name` VARCHAR(255) NOT NULL,
      `email` VARCHAR(255) NOT NULL,
      `password` VARCHAR(255) NOT NULL,
      `created_at` DATETIME NOT NULL,
      `updates_at` DATETIME NOT NULL,
      PRIMARY KEY (`id`),
      UNIQUE INDEX `first_name_UNIQUE` (`first_name` ASC),
      UNIQUE INDEX `last_name_UNIQUE` (`last_name` ASC),
      UNIQUE INDEX `email_UNIQUE` (`email` ASC),
      UNIQUE INDEX `password_UNIQUE` (`password` ASC),
      UNIQUE INDEX `created_at_UNIQUE` (`created_at` ASC),
      UNIQUE INDEX `updates_at_UNIQUE` (`updates_at` ASC))
      ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `mydb`.`messages`
-- -----------------------------------------------------
    CREATE TABLE IF NOT EXISTS `mydb`.`messages` (
      `id` INT NOT NULL AUTO_INCREMENT,
      `users_id` INT NOT NULL,
      `message` TEXT NOT NULL,
      `created_at` DATETIME NOT NULL,
      `updated_at` DATETIME NOT NULL,
      PRIMARY KEY (`id`),
      INDEX `fk_messages_users_idx` (`users_id` ASC),
      UNIQUE INDEX `id_UNIQUE` (`id` ASC),
      UNIQUE INDEX `users_id_UNIQUE` (`users_id` ASC),
      UNIQUE INDEX `message_UNIQUE` (`message` ASC),
      UNIQUE INDEX `created_at_UNIQUE` (`created_at` ASC),
      UNIQUE INDEX `updated_at_UNIQUE` (`updated_at` ASC),
      CONSTRAINT `fk_messages_users`
        FOREIGN KEY (`users_id`)
        REFERENCES `mydb`.`users` (`id`)
        ON DELETE NO ACTION
        ON UPDATE NO ACTION)
      ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `mydb`.`comments`
-- -----------------------------------------------------
    CREATE TABLE IF NOT EXISTS `mydb`.`comments` (
      `id` INT NOT NULL AUTO_INCREMENT,
      `users_id` INT NOT NULL,
      `messages_id` INT NOT NULL,
      `comment` TEXT NOT NULL,
      `created_at` DATETIME NOT NULL,
      `updated_at` DATETIME NOT NULL,
      PRIMARY KEY (`id`),
      INDEX `fk_comments_users1_idx` (`users_id` ASC),
      INDEX `fk_comments_messages1_idx` (`messages_id` ASC),
      UNIQUE INDEX `id_UNIQUE` (`id` ASC),
      UNIQUE INDEX `users_id_UNIQUE` (`users_id` ASC),
      UNIQUE INDEX `messages_id_UNIQUE` (`messages_id` ASC),
      UNIQUE INDEX `comment_UNIQUE` (`comment` ASC),
      UNIQUE INDEX `created_at_UNIQUE` (`created_at` ASC),
      UNIQUE INDEX `updated_at_UNIQUE` (`updated_at` ASC),
      CONSTRAINT `fk_comments_users1`
        FOREIGN KEY (`users_id`)
        REFERENCES `mydb`.`users` (`id`)
        ON DELETE NO ACTION
        ON UPDATE NO ACTION,
      CONSTRAINT `fk_comments_messages1`
        FOREIGN KEY (`messages_id`)
        REFERENCES `mydb`.`messages` (`id`)
        ON DELETE NO ACTION
        ON UPDATE NO ACTION)
    ENGINE = InnoDB;


    SET SQL_MODE=@OLD_SQL_MODE;
    SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
    SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;

Answer 1

InnoDB 索引的最大长度默认为 767 字节。

当您在最大长度为 65535 字节的 TEXT 列上声明唯一索引时，它超出了最大索引长度很多。

UNIQUE INDEX `message_UNIQUE` (`message` ASC),

您可以启用 innodb_large_prefix，这使得创建 3072 字节的索引成为可能，这对于完整的 TEXT 列来说也太小了。

您可以为 TEXT 列使用前缀索引，但这不是强制唯一性的好解决方案。

INDEX `message` (`message`(255) ASC),

您应该重新考虑是否需要对 TEXT 列进行唯一约束。

另见:

• > https://dev.mysql.com/doc/refman/5.7/en/innodb-restrictions.html
• > https://stackoverflow.com/a/16474039/20860