Mysql 左表中不匹配行的SQL联合查询

我有两张桌子，sfuser和membership

sfuser得到139，会员表得到50

我需要查询来选择谁不是任何项目的成员，这意味着89名成员

这是我的问题

select sfuser.id,sfuser.username,sfuser.email from sfuser INNER JOIN projectmembership ON sfuser.id = projectmembership.member_id ;

但是我得到了50个用户，他们是我想要的另一种方式的成员

请洒点光

致意 萨提斯

它应该返回所有不在projectmembership表中的用户

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它应该返回所有不在projectmembership表中的用户。

内部联接将只生成与这两个表匹配的行。。您可以做左联接并筛选出空白记录。比如：

SELECT sfuser.id,
sfuser.username,
sfuser.email
FROM sfuser LEFT JOIN projectmembership ON sfuser.id = projectmembership.member_id
WHERE (projectmembership.member_id is null);

---

内部联接将只生成与两个表匹配的行。。您可以做左联接并筛选出空白记录。比如：

SELECT sfuser.id,
sfuser.username,
sfuser.email
FROM sfuser LEFT JOIN projectmembership ON sfuser.id = projectmembership.member_id
WHERE (projectmembership.member_id is null);

---

内部联接将返回在两个表之间共享联接所用值的所有行。看

您要查找的是左联接，即左表中所有在右表中不匹配的行

select sfuser.id,
  sfuser.username,
  sfuser.email 
from sfuser 
LEFT JOIN projectmembership 
  ON sfuser.id = projectmembership.member_id

---

内部联接将返回在两个表之间共享联接所用值的所有行。看

您要查找的是左联接，即左表中所有在右表中不匹配的行

select sfuser.id,
  sfuser.username,
  sfuser.email 
from sfuser 
LEFT JOIN projectmembership 
  ON sfuser.id = projectmembership.member_id

---

如果sfuser记录可以在项目成员资格表中多次出现，则忘记外部联接-不存在是您想要的：

select sid,
       username,
       email
from   sfuser
where  not exists (
         select null
         from   projectmembership
         where  sfuser.id = projectmembership.member_id);

---

如果sfuser记录可以在项目成员资格表中多次出现，则忘记外部联接-不存在是您想要的：

select sid,
       username,
       email
from   sfuser
where  not exists (
         select null
         from   projectmembership
         where  sfuser.id = projectmembership.member_id);

---

多谢大流士和阿比克多谢大流士和阿比克