sql 左连接可能没有关系

Question

我必须从数据库中的 4 个表生成报告

leads
    id
    name
    country
    create_by       #different from lead_call_logs create_by

lead_call_logs
    id
    lead_id
    create_by
    create_datetime

users
    id
    employee_id
    username
    password

employees
    id
    name

我正在使用这个查询

SELECT
    leads.id AS id,
    CONCAT(leads.first_name,' ',leads.surname) AS lead_name,
    leads.country AS country,
    CONCAT(employees.first_name,' ',employees.surname) AS booked_by,
    lead_call_logs.create_datetime
FROM
    leads
        LEFT JOIN lead_call_logs ON leads.id = lead_call_logs.lead_id,
    users,
    employees
WHERE
    lead_call_logs.create_by = users.id AND
    users.employee_id = employees.id

当潜在客户仍然没有任何 lead_call_logs 时，问题就来了。我怎样才能得到所有有或没有 lead_call_logs 的线索，并得到预订它的员工姓名？

提前致谢。

更新问题

如果在 create_by 中也有一个 create_by 并且 create_by 在 lead_call_logs 中的 create_by <> create_by 怎么办（不同的人在做）

Answer 1

为什么你 "stop" 在第一个 LEFT JOIN 之后？对其他表执行相同操作：

SELECT
    leads.id AS id,
    CONCAT(leads.first_name,' ',leads.surname) AS lead_name,
    leads.country AS country,
    CONCAT(employees.first_name,' ',employees.surname) AS booked_by,
    lead_call_logs.create_datetime
FROM
    leads
        LEFT JOIN lead_call_logs ON leads.id = lead_call_logs.lead_id
        LEFT JOIN users ON lead_call_logs.create_by = users.id
        LEFT JOIN employees ON users.employee_id = employees.id

sql 左连接可能没有关系

sql left join possible no relationship

sql

left-join

更新问题