select id, (c1 + c2) as s

from t1

where s > 100 

select id, (c1 + c2) as s

from t1

where (c1 + c2) > 100 

select t2.*

from (select id, (c1 + c2) as c from t1) t2

where c > 100

 

  --或者

 

select t2.*

from (select id, c = c1+c2 from t1) t2

where c > 100