Calculates HASH of the given string. Length of the returned HASH is always the same.

SELECT
    SHA2('passwd', 256) password_hash

The Result of the function with

256

will always be ``64 characters long alphanumeric string. In this example the result will be:

0d6be69b264717f2dd33652e212b173104b4a647b7c11ae72e9885f11cd312fb

Note: We can never get back to the original value. There is no way to undo the hashing calculation