mysql custom global defined variable

Question

In my database design, I tend to store some variable that is meant to be acting as a ROLE or TYPE as SMALLINT. For example :

Answer 1

I suggest using MySQL variables:

SET HOUSE_SMALL_TYPE = 0;
SET HOUSE_MEDIUM_TYPE = 1;

Then, in your queries you may use these variables:

SELECT * FROM house  WHERE type = @HOUSE_SMALL_TYPE;

This method defines session variables:

If you change a session system variable, the value remains in effect until your session ends or until you change the variable to a different value. The change is not visible to other clients.

If you want to define global MySQL variables (available to all sessions):

SET GLOBAL HOUSE_SMALL_TYPE = 0;
SET GLOBAL HOUSE_MEDIUM_TYPE = 1;

To indicate explicitly that a variable is a global variable, precede its name by GLOBAL or @@global.. The SUPER privilege is required to set global variables.

Documentation:
SET statement
Using system variables
User-defined variables