Insert multiple rows using Cursors.

Question

I am trying to insert rows into a table based on information from another table.
For example:
When Table 1: Num_Rows = 100 my proc will insert 100 rows into Table 2 with relevent data.
Do I need to use a Cursor and iterate through Num_Rows doing an INSERT each time? Is there a better way to do it other than using Cursors?
Rob.

Answer 1

It is not about using cursors or not using cursors. All SQLs wind up as cursors in the Oracle Shared Pool. So there is no such concept as not using cursors. Oracle needs to parse and compile and execute SQLs as cursors.
The issue is WHERE* you do the work?
Do you use the cursor (SQL) to do it for you? Or do you pull the data into another language, like PL or Java and process it there?
And the performance mantra in this case is a very fundemantal Maximize SQL and minimize PL/Java/etc+.
So do not do in PL/SQL what you can do in SQL only. It is a lot slower to pull data from the SQL engine into the PL engine. And then push that very same data from the PL engine back to the SQL engine. Like the following for example:
-- poor design, poor performance
for employee in (select e.* from emp e where e.deptid = 123 )
loop
  insert into tab2 values( employee.empid, employee.name );
end loop;You do not need to use PL (or Java) in this case. The SQL language is more than able to do this better and faster than any other language... as it is closer to the data.
So the following is far more optimal code. Instead of the above PL/SQL code, we can simply do it as:
-- optimal design: maximizing SQL and letting it to as much of the work as possible
insert into tab2 select e.empid, e.name from emp e where e.deptid = 123;