I'm coming from a SQL Server background also and spent the past 2 weeks figuring out how to run scripts like this in IBM Data Studio. Hope it helps.
CREATE VARIABLE v_lookupid INTEGER DEFAULT (4815162342); --where 4815162342 is your variable data
SELECT * FROM DB1.PERSON WHERE PERSON_ID = v_lookupid;
SELECT * FROM DB1.PERSON_DATA WHERE PERSON_ID = v_lookupid;
SELECT * FROM DB1.PERSON_HIST WHERE PERSON_ID = v_lookupid;
DROP VARIABLE v_lookupid;