执行以下命令时:
ALTER TABLE `mytable` ADD UNIQUE (
`column1` ,
`column2`
);
我得到了这个错误信息:
#1071 - Specified key was too long; max key length is 767 bytes
columnn1和column2的信息:
column1 varchar(20) utf8_general_ci
column2 varchar(500) utf8_general_ci
我认为varchar(20)只需要21个字节，而varchar(500)只需要501个字节。所以总字节数是522，小于767。为什么我得到了错误消息?
#1071 - Specified key was too long; max key length is 767 bytes
当前回答
如果您最近修改了innodb_log_file_size，请尝试恢复之前的值。
其他回答
如果你要创建如下内容:
CREATE TABLE IF NOT EXISTS your_table (
id int(7) UNSIGNED NOT NULL AUTO_INCREMENT,
name varchar(256) COLLATE utf8mb4_bin NOT NULL,
PRIMARY KEY (id),
UNIQUE KEY name (name)
) ENGINE=INNODB DEFAULT CHARSET=utf8mb4 AUTO_INCREMENT=1 ROW_FORMAT=FIXED;
应该是这样的
CREATE TABLE IF NOT EXISTS your_table (
id int(7) UNSIGNED NOT NULL AUTO_INCREMENT,
name varchar(256) COLLATE utf8mb4_bin NOT NULL,
PRIMARY KEY (id)
) ENGINE=INNODB DEFAULT CHARSET=utf8mb4 AUTO_INCREMENT=1 ROW_FORMAT=FIXED;
但是您需要从代码中检查该列的唯一性，或者添加一个新列作为varchar列的MD5或SHA1
我发现这个查询在检测哪些列的索引违反了最大长度方面很有用:
SELECT
c.TABLE_NAME As TableName,
c.COLUMN_NAME AS ColumnName,
c.DATA_TYPE AS DataType,
c.CHARACTER_MAXIMUM_LENGTH AS ColumnLength,
s.INDEX_NAME AS IndexName
FROM information_schema.COLUMNS AS c
INNER JOIN information_schema.statistics AS s
ON s.table_name = c.TABLE_NAME
AND s.COLUMN_NAME = c.COLUMN_NAME
WHERE c.TABLE_SCHEMA = DATABASE()
AND c.CHARACTER_MAXIMUM_LENGTH > 191
AND c.DATA_TYPE IN ('char', 'varchar', 'text')
您可以添加长列的md5列
为了解决这个问题，这个方法对我很有效。
ALTER DATABASE dbname CHARACTER SET utf8 COLLATE utf8_general_ci;
索引长度& MySQL / MariaDB
Laravel默认使用utf8mb4字符集，其中包括在数据库中存储“表情符号”的支持。如果您运行的MySQL版本比5.7.7版本更老，或者MariaDB版本比10.2.2版本更老，您可能需要手动配置由迁移生成的默认字符串长度，以便MySQL为它们创建索引。你可以在AppServiceProvider中调用Schema::defaultStringLength方法来配置:
use Illuminate\Support\Facades\Schema; /** * Bootstrap any application services. * * @return void */ public function boot() { Schema::defaultStringLength(191); } Alternatively, you may enable the innodb_large_prefix option for your database. Refer to your database's documentation for instructions on how to properly enable this option. Reference from blog : https://www.scratchcode.io/specified-key-too-long-error-in-laravel/ Reference from Official laravel documentation : https://laravel.com/docs/5.7/migrations
