我有四个表分别是users(id,name)
、roles(id,name)
、members(project_id,user_id,id)
和member_roles(member_id, role_id)
。那么如何同时从此表中选择 users.name 和 roles.name(project_id是准确选择我们需要的名称的条件)?我可以分别选择 users.name 和 roles.name,但是当我连接两个查询时,我的代码失败了。这是获取 users.name 的查询
select users.name from users
inner join members on members.user_id = users.id
where project_id = 1
这是获取 roles.name 的查询
select roles.name from roles
inner join member_roles on member_roles.role_id = roles.id
join members on members.id = member_roles.member_id
where project_id = 1
你快到了。此外,为避免歧义,请在列 Name
上提供别名。
SELECT DISTINCT
u.Name AS member_name,
r.Name AS role_name
FROM users u
INNER JOIN members m
ON u.id = m.user_id
INNER JOIN member_roles mr
ON m.id = mr.member_id
INNER JOIN roles r
ON r.id = mr.role_id
WHERE m.project_id = 1
你如何连接 2 个查询?像这样的事情怎么样:
select u.name as user_name, r.name as role_name from users u join members m on m.user_id = u.id join member_roles mr on mr.member_id = m.id join roles r on r.id = mr.role_id where m.project_id = 1;