SQL并集和排序方式

我有一个恼人的SQL语句，看起来很简单，但看起来太满了。 我希望sql返回一个排序为userdata的resultset，这样，如果某个用户的emailaddress在companys表中，那么该用户就是resultset的第一行

我有一个返回我想要的东西的SQL，但我觉得它看起来很糟糕：

select 1 as o, * 
from Users u
where companyid = 1
and email = (select email from companies where id=1)
union 
select 2 as o, * 
from Users u
where companyid = 1
and email <> (select email from companies where id=1)
order by o

它的方式比我的更优雅。谢谢Richard L

这样行吗？：

select c.email, * 
from Users u
     LEFT JOIN companies c on u.email = c.email
where companyid = 1
order by c.email desc
-- order by case when c.email is null then 0 else 1 end

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我不确定这是否更好，但这是另一种方法

select *, (select count(*) from companies where email = u.email) as o 
from users u 
order by o desc

编辑：如果在不同的公司之间有许多匹配的电子邮件，而您只对给定的公司感兴趣，那么这将成为

select *, 
 (select count(*) from companies c where c.email = u.email and c.id = 1) as o 
from users u 
where companyid = 1
order by o desc

---

你可以这样做

        select CASE 
                WHEN exists (select email from companies c where c.Id = u.ID and c.Email = u.Email) THEN 1 
                ELSE 2 END as SortMeFirst,   * 
    From Users u 
    where companyId = 1 
    order by SortMeFirst

---

您使用的是哪种RDBMS（Oracle、SQLserver…）您需要在JOIN子句中添加Users.companyid=companyid，注意这不是最佳解决方案，因为您在本例中的select将对每个返回的行运行一次。这可能会导致巨大的性能问题

        select CASE 
                WHEN exists (select email from companies c where c.Id = u.ID and c.Email = u.Email) THEN 1 
                ELSE 2 END as SortMeFirst,   * 
    From Users u 
    where companyId = 1 
    order by SortMeFirst