difference between UNHEX and X (MySQL)

Question

What really is the difference between MySQL UNHEX and X when dealing with hexadecimal values in a database?

Eg.

SELECT * FROM test WHERE guidCol IN (UNH         


        

Answer 1

Note that even in MySQL 5.6, the X'' notation has a length limit in the reference mysql client and UNHEX() does not (appear to). I do not know what the limit is for X'', as it is not officially documented but I have encountered it when trying to INSERT a BLOB. With X'' literal, mysql client threw a syntax error with a sufficiently long hex sequence while UNHEX() of the same sequence did not. Obviously, length is not an issue when it comes to an actual GUID, but I figured this is useful for anyone else using this question to answer mysql insertion of binary data in the general case.