oracle多结果集嵌套循环处理优化
--性能差
begin
for a in (select id,name,sex,idcard from people) loop
for b in (select id,name,sex,idcard from english) loop
if a.idcard = b.idcard then
--do something
end if;
end loop;
end loop;
end; --性能优：将多表合并成一个结果集，避免嵌套循环
begin
for a in (select p.id,p.name,p.sex,p.idcard from people p,english e where p.idcard = e.idcard) loop
--do something
end loop;
end;