下表描述了每种标识符类型的最大长度。The following table describes the maximum length for each type of identifier.

在 CREATE VIEW 语句中，列名的别名会检查最大列长度是否为 64 个字符（而不是最大别名长度 256 个字符）。Aliases for column names in CREATE VIEW statements are checked against the maximum column length of 64 characters (not the maximum alias length of 256 characters).

对于不包含约束名称的约束定义，服务器会内部生成一个名称，该名称来源于相关的表名。例如，内部生成的外键和 CHECK 约束名称由表名加上 _ibfk_ 或 _chk_ 及一个数字组成。如果表名接近约束名称的长度限制，为约束名称所需的额外字符可能会导致该名称超过限制，从而导致错误。For constraint definitions that include no constraint name, the server internally generates a name derived from the associated table name. For example, internally generated foreign key and CHECK constraint names consist of the table name plus _ibfk_ or _chk_ and a number. If the table name is close to the length limit for constraint names, the additional characters required for the constraint name may cause that name to exceed the limit, resulting in an error.

标识符使用 Unicode (UTF-8) 存储。这适用于表定义中的标识符以及存储在 mysql 数据库的授权表中的标识符。授权表中标识符字符串列的大小以字符为单位。您可以使用多字节字符，而无需减少这些列中允许存储值的字符数。Identifiers are stored using Unicode (UTF-8). This applies to identifiers in table definitions and to identifiers stored in the grant tables in the mysql database. The sizes of the identifier string columns in the grant tables are measured in characters. You can use multibyte characters without reducing the number of characters permitted for values stored in these columns.

MySQL 帐户名中的值，例如用户名和主机名，是字符串，而不是标识符。有关这些值在授权表中存储的最大长度的信息，请参见 授权表范围列属性。Values such as user name and host names in MySQL account names are strings rather than identifiers. For information about the maximum length of such values as stored in grant tables, see Grant Table Scope Column Properties.