Implementing a c/c++ style union as a column in MySQL

As a1ex07 said, you CAN do it by storing string representation. But if you are worried about space, storing real values in several NULLable columns will probably save more space.

Alternately, create ancillary tables and normalize, e.g.

Your want:

TABLE1
|id|name_or_TK#|

Your can do:

TABLE1
|id|name|TK|

or you can do

TABLE1
|id|ST_or_human_flag|other columns common to humans and stormtroopers

TABLE2 - Names_of_humans
|id|name|

TABLE3 - TKs_of_STs
|id|TK|