What data type should I use: ENUM, TINYINT, or CHAR? I'm creating a new table and I would like to do it right. The table will be a list of members with their Professional Type and Decile associated. 

The Professional Type is a 3-character string. There are only 8 allowable strings for this field. Should I use ENUM or CHAR(3) or something better?

The Decile can be any number between 1-10, but only these numbers. Should I use ENUM or unsigned TINYINT or something better?

Which are the best options for efficiency?
ENUMs scare me because of any issue regarding adding/removing type values. You are probably better off representing both ProfessionalType and Decile as TINYINT or CHAR(3). Anything but ENUM.

See my past posts on ENUM :


Ocy 19, 2011 : Advantages and Disadvantages to using ENUM vs Integer types?
Jan 24, 2012 : Is it possible to change ENUM() lists?


For efficiency, please do not index this field alone, given such a low cardinality (8,10).