Re: SHA-256 which data type is the best?

[Rick James]

Plan A: Hex representation:
BINARY(64)

Plan B: Binary representation:
BINARY(32)
This has the complication of storing binary values. Use some escaping mechanism (see your language specifics) for INSERTing.
Drawback: SELECT * (etc) would produce gibberish. Workaround: SELECT HEX(sha_col)...
Advantage: This is the most compact.

Plan C: Base64
BINARY(43)
Some languages make it easy to build a base-64 string. Note: there will be upper and lower case letters, so case folding is a no-no.
This one is a compromise between human-readable and compact.

Why "BINARY"? You don't need utf8 collation, etc, so BINARY instead of CHAR. The size does not vary, so not VAR. Add NULL or NOT NULL as needed.

Plan D: Use MD5 instead; it is unique enough. BINARY(16/22/32)