Use Sum aggregate function with case statement as below, if you want sum of those t.value based on t.clock then do group by on that column so that you will get clock while sum of values.

select sum(case when  i.hostid='223344'   and t.itemid = '0223344' then t.value end) as FirstValue,sum(case when  i.hostid='112233' and t.itemid = '0112233' then t.value end) as SecondValue
from hosts h, items i,history_uint t
where i.hostid=h.hostid and t.itemid=i.itemid
If it is based on t.clock then

   select t.clock, sum(case when  i.hostid='223344'   and t.itemid = '0223344' then t.value end) as FirstValue,sum(case when  i.hostid='112233' and t.itemid = '0112233' then t.value end) as SecondValue
    from hosts h, items i,history_uint t
    where i.hostid=h.hostid and t.itemid=i.itemid
    group by t.clock
    0

You can try this below logic-

SELECT i.hostid,t.itemid,t.value as OneValues, t.clock as time
FROM hosts h 
INNER JOIN items i 
    ON i.hostid=h.hostid
    AND i.hostid IN ('223344','112233')
    AND i.itemid IN ('0223344','0112233')
INNER JOIN  history_uint t 
    ON t.itemid=i.itemid