VARCHAR vs. CHAR in MySQL: When Should You Use Which?

MySQL database design: choice of VARCHAR and CHAR

In MySQL database design, choosing VARCHAR or CHAR data type will affect performance and storage efficiency. This article will dive into their differences:

Comparison of VARCHAR and CHAR

特性	VARCHAR	CHAR
数据类型长度	可变长度	固定长度
存储空间	存储实际数据长度	始终分配最大指定长度
存储效率	数据长度变化时效率较高	数据长度较短时效率较低
存储碎片	可能导致存储碎片	存储一致，减少碎片

For example, to store fixed-length MD5 hashes (32 characters), CHAR is more appropriate. Using CHAR ensures that all MD5 hashes occupy the same storage space, reducing fragmentation and potentially improving performance.

For more details and a comprehensive comparison, please refer to the MySQL official documentation on [CHAR and VARCHAR data types](https://www.php.cn/link/2f4cd0a689df7a6613b9ff4e84b34df6).

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