请问两个表外连接怎么做

请教这个怎么做 mysql

员工表和客户表没有关联字段吧

SELECT
    employee_id AS id,
    employee_name AS NAME,
    '员工' AS type
FROM
    employee
UNION
    SELECT
        customer_id AS id,
        customer AS NAME,
        '客户' AS type
    FROM
        customer

利用union 连接即可