You would expect the SQL 
world to be standardized, but you will find wide 
disparities in implementations and dialects.  ENUM is a case in point.  In 
PostgreSQL, the ENUM type is actually a data type separate from the built in 
NUMERIC and TEXT data types, so the regular numeric and string operators and 
functions don't work on it.  Contrastingly, in MySQL, ENUM is defined as a 
string object, where you can use LIKE.  The inconsistencies can be maddening 
for DBAs, particularly when trying to change to a different database system.

    Richard Sims