Compare table A and table B and update table B ,,,,table B has 300k rows

Question

Hi,
I m trying to write a code, I have tables A and table B.
I need to compare table A and table B , and update table B with one column.
using joins b/w A&B tables, I selected one record from table A in cursor.
After Begin I m trying to open cursor and in FOR LOOP
Im trying to update table B WHERE CURRENT OF Cursor.
this is erroring out.
could you let me know on this.
there is another way like selecting required columns from both table.but i was told to do as above.
Thanks

Answer 1

> this is erroring out.
You haven't posted nearly enough for anyone to help you.  You didn't even tell us what error you are getting.
So about the only thing we can do is post a generic MERGE statement which you'll have to modify for your use.
merge into tableB b
using (select some_key, some_column from tableA where etc.) u
on (u.some_key = b.some_key)
when matched then update
set b.some_column = u.some_column;