Wondering how much actual storage space will be taken up by these two datatypes, as the MySQL documentation is slightly unclear on the matter.
CHAR(M) M × w bytes, 0 <= M <= 255, where w is the number of bytes required for the maximum-length character in the character set
VARCHAR(M), VARBINARY(M) L + 1 bytes if column values require 0 – 255 bytes, L + 2 bytes if values may require more than 255 bytes
This seems to imply to me that, given a utf8-encoded database, a CHAR will always take up 32 bits per character, whilst a VARCHAR will take between 8 and 32 depending on the actual byte length of the characters stored. Is that correct? Or does a VARCHAR imply an 8-bit character width, and storing multi-octet UTF8 characters actually consumes multiple 'characters' from the VARCHAR? Or does the VARCHAR also always store 32 bits per character? So many possibilities.
Not something I've ever had to worry this much about before, but I'm starting to hit in-memory temp table size limits and I don't necessarily want to have to increase MySQL's available pool (for the second time).