create VIEW in mysql from two tables

Question

I have a table with users for my mail server. This table for imap authenication in dovecot:

+-------------+------------------+-------------------+------------------+------+------+---------------------------------------+--------+---------+---------------------------+
| user_name   | domain_name      | passwd            | pwd_hash         | uid  | gid  | mailbox_basepath                      | enable | quota   | desc_rec                  |
+-------------+------------------+-------------------+------------------+------+------+---------------------------------------+--------+---------+---------------------------+
| logistic    | piduna.pp.ua     | loG-1990M         | _no_hash_passwd_ | 2000 | 2000 | /home/maildir/piduna.pp.ua/           |      1 | 2048000 | box for logistic          |
| 1c          | piduna.pp.ua     | 1c_user_1c        | _no_hash_passwd_ | 2000 | 2000 | /home/maildir/piduna.pp.ua            |      1 | 2048000 | Denisyuk V.V.             |
| admin       | piduna.pp.ua     | AAddMmM1N         | _no_hash_passwd_ | 2000 | 2000 | /home/maildir/piduna.pp.ua            |      1 | 2048000 | Admin                     |
| al.service  | piduna.pp.ua     | Alumo_Serv4321    | _no_hash_passwd_ | 2000 | 2000 | /home/maildir/piduna.pp.ua            |      1 | 2048000 | Alumo Service             |

I need to create table with two columns. First column, all@piduna.pp.ua. Second column it is all my email accounts. In one table, I know how make concatenation from user_name and domain_name. Look:

CREATE VIEW `forwardings_all_view` AS select lcase(concat(`users`.`user_name`,'@',`users`.`domain_name`)) AS `email_fqn` from `users` where (`users`.`enable` = 1)

But, how to add in it VIEW, second column: all@piduna.pp.ua.

Like that:

+------------------------------+-------------------------------------------------+
| email_fqn                    | source                                          | 
+------------------------------+-------------------------------------------------+
| .logistic@piduna.pp.ua       | all@piduna.pp.ua                                | 
| 1c@piduna.pp.ua              |                                                 | 
| admin@piduna.pp.ua           |                                                 |
| al.service@piduna.pp.ua      |                                                 | 

Answer 1

Try this:

create view first_user as
select user_name from users where enable limit 1;

create view forwardings_all_view as
select lcase(concat(a.`user_name`,'@',a.`domain_name`)) AS `email_fqn`,
  if(b.user_name is null, '', 'all@piduna.pp.ua') `source`
from `users` a
left join first_user b on a.user_name = b.user_name
where a.`enable` = 1;

fiddle