Question

declare begin   for i in (select * from emp)   loop     if i.sal=1300 then       update emp       set sal=13000;     end if;   end loop; end; 

This code is updating all the records with salary 13000.
Instead i want to update records having salary 1300 to the value 13000.
Can you tell where I made a mistake?
I am accesing records using implicit cursor..
for every record i am checking the sal value of that record..
if salary value in a particular record is 1500 i want to update it to 15000..

Answer 1

Whenever you can do the update with one single statement, you should do that instead of using a loop. You’ll get a very huge performance gain that way; or, the other way round, updates in a loop cost you a lot of performance.

If you really really have to use a loop, of course you need a where condition to make sure you are only updating the record you really want to update. A possible way that always works (even if there is no unique key available) is to use the rowid pseudocolumn:

begin   for i in (select rowid, emp.* from emp)   loop     if i.sal=1300 then       update emp       set sal=13000       where rowid=i.rowid;     end if;   end loop; end; 

Another possibility would be using an explicit cursor and the ‘update … where current of cursorname‘ syntax.