MySQL 8.0

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CREATE TABLE messages (messageid INTEGER PRIMARY KEY AUTO_INCREMENT
                       , message VARCHAR(150)
                       , sender VARCHAR(40)
                       , recipient VARCHAR(40))

CREATE TABLE employees (employeeid INTEGER PRIMARY KEY
                        , employeename VARCHAR(40)
                        , area VARCHAR(40))
insert into employees values (1, 'Mark', 'Maintenance')
insert into employees values (2, 'Ann', 'Maintenance')
INSERT INTO messages (message
                      , sender
                      , recipient) 
VALUES ("Message."
        , "System"
        , (SELECT employeename
           FROM employees 
           WHERE area = "Maintenance"
           and employeeid = 1))
INSERT INTO messages (message
                      , sender
                      , recipient) 
VALUES ("Message."
        , "System"
        , (SELECT max(employeename)
           FROM employees 
           WHERE area = "Maintenance"))
select * from messages


messageid
message
sender
recipient


1
Message.
System
Mark

2
Message.
System
Mark