MySQL 8.0

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CREATE TABLE messages (messageid INTEGER PRIMARY KEY
                       , 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 messages (message
                      , sender
                      , recipient) 
VALUES ('Message.'
        , 'System'
        , (SELECT employeename 
           FROM employees 
           WHERE area = 'Maintenance'))
Field 'messageid' doesn't have a default value

INSERT INTO messages (messageid
                      , message
                      , sender
                      , recipient) 
VALUES (1
        , 'Message.'
        , 'System'
        , (SELECT employeename 
           FROM employees 
           WHERE area = 'Maintenance'))
select * from messages


messageid
message
sender
recipient


1
Message.
System
Mark