SQL：如何按字母顺序排序联合？

Question

这是一个有点奇怪的用例，但是你如何按字母顺序排列这样一个简单联合的结果呢？

select name 
from Reviewer
union
select model
from Car; 

Answer 1

具有讽刺意味的是，在许多数据库中，您的查询将按字母顺序返回值。排序是在union重复删除期间完成的。

当然，你不能依赖它。因此，您应该包含order by子句：

select name 
from Reviewer
union
select model
from Car
order by name;

order by适用于完整的union。列名来自第一个子查询。

Answer 2

select val
from (
  select name as val 
  from Reviewer

  union

  select model as val
  from Car
) as x
order by val

Answer 3

以下是设置alias和ORDER BY的方法：

SELECT 
  name AS NameModel
FROM Reviewer
UNION
SELECT  
  model AS NameModel
from Car
ORDER BY 
 NameModel;

在ORDER BY之后评估UNION。

Answer 4

你的sql：

select name 
from Reviewer
union
select model
from Car;

答案1：

select name from Reviewer
union
select model from Car
order by name;

答案2：

select * from
    (select name "id" from Reviewer
    union
    select model from Car) x
order by x.id;

Answer 5

select val
from (
  select name as val 
  from Reviewer

  union

  select model as val
  from Car
) as x
order by val

我的答案和以上都是一样的。在SQL中，我们可以用不同的方式编写。

我们也可以忽略as运算符。