How to imporve perofmance

Question

Hi,
I am having insert query with select as mentioned below which takes long time to execute due to huge data.
Insert into compaign_pipe(x1,x2,x3,..............etc)
select rownum,a.* from (
select * from  lead_opty   where ....;
union all
select * from gom_fcrm    where....
union all
select * from compaign_lead  where...
union all
select * from claims_lead      where
) a;
can you please suggest how can i improve the performance
or
if i try same as mentioned below will it increase the performance
Insert into compaign_pipe(x1,x2,x3,..............etc)
select * from  lead_opty   where ....;
Insert into compaign_pipe(x1,x2,x3,..............etc)
select * from  gom_fcrm  where ....;
Insert into compaign_pipe(x1,x2,x3,..............etc)
select * from  compaign_lead where ....;
Insert into compaign_pipe(x1,x2,x3,..............etc)
select * from  claims_lead where ....;
Thanks and regards,
Ibrahim Sayyed.

Answer 1

I am having insert query with select as mentioned below which takes long time to execute due to huge data.
I suggest that you don't do anything until you determine that you actually have a performance issue.
Then don't do anything until you determine what the cause of that issue is.
You are inserting into ONE table and get data from FOUR tables using FOUR queries.
The INSERT could be the issue - there might be a lot of indexes, referential constraints or triggers.
Any, or all, of the four queries could be the issue - any of them might be using poor execution plans due to lack of statistics, lack of indexes, etc.
You need a LOT more information before you start trying to 'solve' the problem.
IMHO the simplest way to start is to forget the INSERT for now and work with each of the SELECT queries one at a time.
1. Create an execution plan for one of the queries and see if you spot any possible issues.
2. Execute the query and see how long it takes to execute.
3. Tune the query as indicated by the execution plan or the sql tuning advisor.