What is the best way to store long hex string that has more then 1500 chars?
What is the best type?
BYTEhave fixed padding and a maximum length of 255 byte, so it's no good for you.
TEXThave both a maximum length of 65535 bytes (64kB) and uses 2 more extra bytes to store the length of the data.
LONGTEXThave a maximum length of 4294967295 bytes (4GB) and uses 4 more extra bytes to store the length of the data.
If you know that you will always have less than 64kB of data in your HEX string, I would choose
TEXT, otherwise go with