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mysql 建表报错 Specified key was too long; max key length is 767 bytes

2024-06-27 11:56:04  阅读:203  来源: 互联网

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This error occurs in MySQL when you are trying to create an index on a column that exceeds the maximum index length allowed.

To resolve this issue, you can do one of the following:

  1. Use a Prefix Index: If you are creating an index on a VARCHAR column, you can specify a length for the index to reduce the key length. For example, instead of indexing the entire VARCHAR column, you can index the first few characters by specifying a length in the index definition.

    CREATE TABLE example_table (
        column_name VARCHAR(255)
    );
    
    CREATE INDEX index_name ON example_table(column_name(191));
    

    SQL

    In this example, the index on the column_name is created with a maximum length of 191 characters (to fit within the 767-byte limit).

  2. Change the Character Set and Collation: If you are using a multi-byte character set like utf8mb4, you can reduce the maximum key length by changing to a single-byte character set like latin1.

    ALTER DATABASE database_name CHARACTER SET = latin1;
    

    SQL

    Changing the character set to latin1 will allow for longer index keys within the 767-byte limit.

  3. Use InnoDB File Format Barracuda: If you are using InnoDB storage engine, you can change the innodb_large_prefix setting to allow longer index key lengths.

    SET GLOBAL innodb_file_format=Barracuda;
    SET GLOBAL innodb_large_prefix=ON;
    

    SQL

    This will enable support for large index key prefixes in InnoDB tables.

Choose the method that best fits your requirements and system configuration to resolve the "Specified key was too long; max key length is 767 bytes" error in MySQL.

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