Mysql case when getting another table - mysql

Question

I have got two tables one is log details and another is user name list.
I can get with "INNER JOIN user_tbl ON log_user_id=user_id" but also I have got a super user id is exception and this exception user isn't in the user table. I am using this user at the back ground the relation with database is level of this user like as 9999.
How can I show the super user as a name like as "Supervisory"?
Example sql:
Table structures are:
CREATE TABLE `user_list_tb` (
`user_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`user_name` varchar(40) COLLATE utf8_turkish_ci NOT NULL,
`user_pwd` varchar(40) COLLATE utf8_turkish_ci NOT NULL,
`user_level` int(11) NOT NULL DEFAULT '0',
`user_owner_id` int(10) unsigned NOT NULL,
`user_datetime` datetime NOT NULL,
`user_change_pwd` tinyint(1) DEFAULT NULL,
`user_pwd_try` int(3) unsigned DEFAULT NULL,
PRIMARY KEY (`user_id`),
UNIQUE KEY `user_name_UNIQUE` (`user_name`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8 COLLATE=utf8_turkish_ci;
CREATE TABLE `log_system_tb` (
`log_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`log_act_name` varchar(10) COLLATE utf8_turkish_ci NOT NULL,
`log_user_id` int(10) unsigned NOT NULL,
`log_datetime` datetime NOT NULL,
`log_message` varchar(256) COLLATE utf8_turkish_ci DEFAULT NULL,
PRIMARY KEY (`log_id`)
) ENGINE=InnoDB AUTO_INCREMENT=49720 DEFAULT CHARSET=utf8 COLLATE=utf8_turkish_ci;
SELECT
log_id,
log_act_name,
log_user_id,
user_name,
log_datetime,
log_message
from log_system_tb
JOIN user_list_tb
ON (log_user_id=user_id)
where log_datetime>="2016-04-01 00:00:00"
and
log_datetime<="2016-04-14 00:00:00"
order by log_id desc limit 1000;
Best regards
Mehmet

Answer 1

You need to use a left join because there will not be a row in the user_list that corresponds to the supervisor's logged events. Also please see the case statement below.
SELECT
log_id,
log_act_name,
log_user_id,
(case when user_id=9999 then 'Supervisory' ELSE user_name END),
log_datetime,
log_message
from log_system_tb
LEFT JOIN user_list_tb
ON (log_user_id=user_id)
where log_datetime>="2016-04-01 00:00:00"
and
log_datetime<="2016-04-14 00:00:00"
order by log_id desc limit 1000;

Answer 2

You can do it like this:
(case when user_id=9999 then 'Supervisory' END)