insert into A(a,b,c)
select * from (
select e,f,g from B where e!=15
union all
select C.e,C.f,C.g from C) t
where exists(select e,f,g from B where e!=15 )
select * from (
select e,f,g from B where e!=15
union all
select C.e,C.f,C.g from C) t
where exists(select e,f,g from B where e!=15 )
SELECT E,F,G FROM B WHERE E!=15
UNION ALL
SELECT E,F,G FROM C
insert into A select e,f,g from B where e!=15 union all select C.e,C.f,C.g from C
select e,f,g from B where e!=15
union all
select C.e,C.f,C.g from C where exists(select e,f,g from B where e!=15)