对于某些ID，从具有多行的表中选择具有标识符值的

Question

我目前有以下结果：

ID    Location
1     NYC
1     LA
2     NYC
3     PIT

我想要以下内容：

ID    Location
1     Multiple
2     NYC
3     PIT

有谁知道一个简单的方法来实现这一目标？

Answer 1

使用case与count和distinct进行此处是一种方法：

select distinct id, 
  case when count(location) over (partition by id ) > 1 
    then 'Multiple' else location end Location
from yourtable

• SQL Fiddle Demo

Answer 2

使用sub-query，COUNT，CASE，GROUP BY：

SELECT mm.id, CASE WHEN mm.count > 1 THEN 'Multiple' ELSE loc END As Location
FROM
(SELECT COUNT(id) As count, id, MAX(location) As loc
FROM myTable
GROUP BY id) As mm;

SQL Fiddle

Answer 3

select ID,case when MIN(name) = MAX(name) then  MIN(name) else 'multiple' end as Location
from <your tabel name>
group by id