What is the Most Efficient Data Type for Storing SHA1 Hash Values in MySQL?

Storing SHA1 Hash Values Efficiently in MySQL

When storing the result of a SHA1 hash in a MySQL database, it's essential to determine the appropriate field type for optimal storage efficiency.

The question arises: what should be the length of the VARCHAR field for storing the hash result?

Answer:

While VARCHAR is suitable for variable-length data, it's not ideal for fixed-length data like a SHA1 hash. A SHA1 value is always 160 bits long, and using VARCHAR would result in an additional byte wasted for the length field.

Additionally, storing the raw SHA1 value is inefficient as it uses 4 bits per character, requiring 40 characters (160/4).

Instead, it's recommended to use the BINARY(20) data type and convert the SHA1 value to binary using the UNHEX function. This method stores the hash in binary format, using 8 bits per character, and requires only 20 characters (160/8).

Storage Comparison:

A comparison between BINARY(20) and CHAR(40) illustrates the efficiency advantage:

With millions of records:

• BINARY(20): 44.56M
• CHAR(40): 64.57M

Using the BINARY(20) data type significantly reduces storage space, making it the preferred choice for storing SHA1 hash values in MySQL.

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