Updating a table from another table

Question

I have a target table a.
SQL> select * from a;
FUND TERM
1
2
3
4
5
6
7
8
8 rows selected.
And, I have another table 'b' where I have the values for 'term' backed up for 4 funds.
SQL> select * from b;
FUND TERM
1 07-JUL-08
2 08-JUL-08
3 09-JUL-08
4 10-JUL-08
4 rows selected.
I could use the below merge sql statement to update the target table 'a' with term dates from table b.
SQL> merge into a
using b
on (a.fund = b.fund)
when matched then
update set a.term = b.term;
Merge successfully completed.
SQL> select * from a;
FUND TERM
1 07-JUL-08
2 08-JUL-08
3 09-JUL-08
4 10-JUL-08
5
6
7
8
8 rows selected.
But, my question is, how could this update be done without using 'merge' in sql (not pl/sql). I think I've done it in the past, but just cannot recall how I did it.
Thanks in advance for any tips you may provide.

Answer 1

A few ways:
update a
set    a.term = (select b.term
                 from   b
                 where  b.fund = a.fund)
where  exists   (select b.term
                 from   b
                 where  b.fund = a.fund)
or
update
   select a.term a_term
         ,b.term b_term
   from   a,b
   where  a.fund = b.fund
set a_term = b_term;The second one only works if you have a "key preserved table".