Oracle UPDATE Question - oracle

Question

Can the update described below be completed in one UPDATE statement?
I want to update the Operators.name_id values with the Users.name_id values by joining on Users.name = Operators.op_name. Both Users.name and Operators.op_name are have a unique.
I know the situation described below doesn't follow "best practices", but it's a much simpler example of what I'm trying to do: namely updating a field with the value from another joined table.
Table: Users
user_id name
----------------
34 Billy
43 Jimmy
50 Joe
Table: Operators (before UPDATE)
op_id op_name user_id
-------------------------
12 Billy 35
35 Jimmy 46
33 Joe 99
Table: Operators (after UPDATE)
op_id op_name name_id
-------------------------
12 Billy 34
35 Jimmy 43
33 Joe 50

Answer 1

UPDATE operators o
SET user_id =
(
SELECT u.user_id
FROM users u
WHERE o.op_name = u.name
)
WHERE o.op_name IN
(
SELECT name
FROM users
)
In Oracle 10g, more efficient:
MERGE
INTO operators o
USING users u
ON (u.name = o.op_name)
WHEN MATCHED THEN
UPDATE
SET user_id = u.user_id

Answer 2

update (
select oo.user_id, uu.user_id uu_id
from operators oo
join
users uu on uu.name = oo.op_name
)
set user_id = uu_id
Here's the full test script (I'm using my_users and my_operators so as not to mess with your data).
drop table my_users;
create table my_users (
user_id number(2),
name varchar2(30) unique
)
;
insert into my_users (user_id, name)
select 34, 'Billy' from dual union all
select 43, 'Jimmy' from dual union all
select 50, 'Joe' from dual
;
drop table my_operators;
create table my_operators (
op_id number(2),
op_name varchar2(30) unique,
user_id number(2)
)
;
insert into my_operators (op_id, op_name, user_id)
select 12, 'Billy', 35 from dual union all
select 35, 'Jimmy', 46 from dual union all
select 33, 'Joe', 99 from dual
;
update (
select oo.user_id, uu.user_id uu_id
from my_operators oo
join
my_users uu on uu.name = oo.op_name
)
set user_id = uu_id
;
select * from my_operators;