wsdydmw
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2014-05-13 17:08

关于Mysql建表的长度限制

已采纳

create table Article (
articleID varchar(255) not null,
articleCotent varchar(255),
articleCreateDate datetime,
articleDescription varchar(255),
articlePV integer,
articlePicUrl varchar(255),
articleTitle varchar(60),
articleType varchar(50),
articleUrl varchar(255),
isShowCover bit,
primary key (articleID)
)
执行以上的建表语句,报错Specified key was too long; max key length is 767 bytes
难道必须要修改表的长度才可以吗?
我的MySql是6.0.11版的

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4条回答

  • leehuat leehuat 7年前

    [code="java"]
    MySQL是限制长度的, 因为你是设置的UTF-8编码,
    articleID 长度是255*4 > 767 的

    mysql官方好像有个说明, 如下
    MySQL has a prefix limitation of 767 bytes in InnoDB, and 1000 bytes in MyISAM. This has never been a problem for me, until I started using UTF-16 as the character set for one of my databases. UTF-16 can use up to 4 bytes per character which means that in an InnoDB table, you can’t have any keys longer than 191 characters. Take this CREATE statement for example:

    CREATE TABLE user (
    id int(11) NOT NULL AUTO_INCREMENT,
    username varchar(32) NOT NULL,
    password varchar(64) NOT NULL,
    email varchar(255) NOT NULL,
    PRIMARY KEY (id),
    UNIQUE KEY UNIQ_8D93D649F85E0677 (username),
    UNIQUE KEY UNIQ_8D93D649E7927C74 (email)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf16 AUTO_INCREMENT=1 ;
    This will fail with an error like Specified key was too long; max key length is 767 bytes, because the UNIQUE INDEX on the email field requires at least 1020 bytes (255 * 4).
    [/code]

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  • taoshi006 taoshi006 7年前

    给字段名都加上"'",就OK

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  • chenxiang105 chenxiang105 7年前

    多大的数据量,主键需要那么大? 换个小点点做主键好了, 搞个ID什么的。

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  • hadeslbf hadeslbf 7年前

    一般主键建议用自增长的bigint,如果不想ID被人可读的话,可以选择32个字符的UUID,也是挺好的。

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