我有3个表:
用户
- 用户ID
- 用户名
预约
- 预约
- useridfk
- 约会名称
- 启动
- 完
叮当
- pid
- useridfk
- 链接
- 项目idfk
我想做的是按用户ID加入所有表格,并显示所有在plinks中存在链接的约会,其中用户username=Mike
试试这样的东西:
select b.* from users a join Appointments b on a.userid=b.useridfk join plinks c on a.userid=c.useridfk where a.username='Mike' and c.plinks is not null
你试过这样的东西吗?
SELECT *
FROM Appointments
INNER JOIN users
ON users.userid = Appointments.useridfk
INNER JOIN plinks
ON users.userid = plinks.useridfk
WHERE users.username = 'Mike'
AND plinks.link IS NOT NULL;
猜测表之间的关系我会这样做:
SELECT appointments.*
FROM users
JOIN appointments ON users.userid = appointments.useridfk
LEFT JOIN plinks ON users.userid = plinks.useridfk
WHERE plinks.useridfk IS NOT NULL
AND users.username = 'Mike'
试试这个
select a.* from Appointments a inner join Users b on b.UserId = a.UserIdFk
b.UserId=c.UserIdFk上的内部联接PL链接c其中b.UserName='Mike'和c.Link不是空
U可以尝试解决您的问题。。。
SELECT * FROM Appointments as a INNER JOIN users as u ON u.userid = a.useridfk INNER JOIN plinks as p ON u.userid = p.useridfk
WHERE u.username = 'Mike' AND p.link IS NOT NULL;