with query1 do
begin
close;
sql.clear;
sql.text := 'select a.c,b.x,c.s from A a,B b,C c' +
'where a.a=b.a and a.b=c.b and a.c=:c';
parambyname('c').asvalue := cValue;
open;
end;
begin
close;
sql.clear;
sql.text := 'select a.c,b.x,c.s from A a,B b,C c' +
'where a.a=b.a and a.b=c.b and a.c=:c';
parambyname('c').asvalue := cValue;
open;
end;
union
select A.*, C.s from A, C where A.b=C.b and A.c=:Value:Value表示参数,也可以用实际值代替