SQL UNION和ORDER BY

Question

我有一个看似简单的烦人的SQL语句，但它看起来awfull。 我想要让某个用户在结果集的第一行，如果用户emailaddress可以在公司表的SQL返回与有序用户数据结果集。

我有这样的SQL返回我想要什么，但我认为它看起来可怕的：

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

和的方式，从用户表中EMAILADDRESS可以在许多企业因此不能是在EMAILADDRESS联接： - （

你有什么想法如何改善这种说法？

林使用Microsoft SQL Server 2000。

编辑： 即时通讯使用这一个：

select *, case when u.email=(select email from companies where Id=1) then 1 else 2 end AS SortMeFirst 
from Users u 
where u.companyId=1 
order by SortMeFirst

其方式比我更优雅。感谢理查德升！

Answer 1

您可以做这样的事情..

        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

Answer 2

将这项工作：

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

Answer 3

我不知道这是更好的，但它是一种替代方法

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

编辑：是否有可能跨越匹配不同的公司许多电子邮件，而你只是在给定的感兴趣的公司，这成为

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