Oracle 11g Release 2

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create table users (
  email varchar2(32) unique
, name varchar2(32)
, id number
);
create table user_details (
  username varchar2(32)
, address varchar2(64)
, details varchar2(64)
, email varchar2(64)
, user_id number 
); 
insert all
  into users (email, name, id) 
    values ('user.mail1@domain.org','name_1',1)
  into users (email, name, id) 
    values ('user.mail2@domain.org','name_2',2)
  into users (email, name, id) 
    values ('user.mail3@domain.org','name_3',3)
--
  into user_details (username, address, details, email, user_id)
    values ('name1','address_1','details_1','user.mail1@domain.org',null)
  into user_details (username, address, details, email, user_id)
    values ('name2','address_2','details_2','user.mail2@domain.org',null)
  into user_details (username, address, details, email, user_id)
    values ('name3','address_3','details_3','user.mail3@domain.org',null)  
select * from dual;
6 rows affected

select * from users;


EMAIL
NAME
ID


user.mail1@domain.org
name_1
1

user.mail2@domain.org
name_2
2

user.mail3@domain.org
name_3
3


select * from user_details ;


USERNAME
ADDRESS
DETAILS
EMAIL
USER_ID


name1
address_1
details_1
user.mail1@domain.org
null

name2
address_2
details_2
user.mail2@domain.org
null

name3
address_3
details_3
user.mail3@domain.org
null


update (
  select user_id, id 
  from user_details UD
    join users U on UD.email = U.email
) 
set user_id = id ; 
3 rows affected

select * from user_details;


USERNAME
ADDRESS
DETAILS
EMAIL
USER_ID


name1
address_1
details_1
user.mail1@domain.org
1

name2
address_2
details_2
user.mail2@domain.org
2

name3
address_3
details_3
user.mail3@domain.org
3

EMAIL	NAME	ID
user.mail1@domain.org	name_1	1
user.mail2@domain.org	name_2	2
user.mail3@domain.org	name_3	3

USERNAME	ADDRESS	DETAILS	EMAIL	USER_ID
name1	address_1	details_1	user.mail1@domain.org	null
name2	address_2	details_2	user.mail2@domain.org	null
name3	address_3	details_3	user.mail3@domain.org	null