sql - 联合查询的结果顺序

Question

我有一个联合查询，它从两个不同的人群中获取计数。如何强制按查询中写入的顺序而不是按升序/降序返回结果？

select count(datediff(yyyy,dob,admitdate) as counts
from myTable
where condition
union
select count(datediff(yyyy,dob,admitdate) as counts
from myTable
where condition

我希望第一个结果始终作为第一行返回。这可能吗？

Answer 1

您必须使用 ORDER BY 子句指定顺序。在您的示例中，您可能会这样做：

SELECT 1 AS seq, COUNT(datediff(yyyy,dob,admitdate) as counts
  FROM myTable
 WHERE ...condition-1...
UNION
SELECT 2 AS seq, COUNT(datediff(yyyy,dob,admitdate) as counts
  FROM myTable
 WHERE ...condition-2...
 ORDER BY seq

Answer 2

select 1, count(datediff(yyyy,dob,admitdate) as counts
from myTable
where condition
union
select 2, count(datediff(yyyy,dob,admitdate) as counts
from myTable
where condition
order by 1