SQL db query: how to add a new field and assign values
Not the most elegant of solutions, but to answer your question, you could do this:

SELECT T1_ID AS ID, T1_NAME AS NAME, T1_ADD AS ADDRESS, 'ANIMAL' AS TYPE
FROM Table1
UNION
SELECT T2_ID AS ID, T2_NAME AS NAME, T2_ADD AS ADDRESS, 'HUMAN' AS TYPE
FROM Table2
UNION
SELECT T3_ID AS ID, T3_NAME AS NAME, T3_ADD AS ADDRESS, 'OBJECT' AS TYPE
FROM Table3