Add ENum Attribute to existing table using Alter I am using oracle XE and trying to add a attribute that restricts to only three  available value 'Small','Medium','large' to an existing table using Alter Table and Enum.

Tried doing,

ALTER TABLE TRUCK ADD TTYPE ENUM('SMALL','MEDIUM','LARGE');


but gets invalid option 

ALTER TABLE TRUCK ADD TTYPE ENUM('SMALL','MEDIUM','LARGE');
                                 *


where the error highlights after ENUM.

I think I am having syntax error. Please help to resolve.
I think you want this:

ALTER TABLE TRUCK 
    ADD (ttype VARCHAR2(6) 
    CONSTRAINT con_type 
    CHECK (ttype in('SMALL','MEDIUM','LARGE'))
    );