选择goup后的第一行

Question

我有下面的查询，它返回一个小于20的类的名称，如果没有小于20的类，则添加一个新的类。问题是，当我从类中删除一个用户时，该查询返回两行。 我只需要获得返回的第一行。

SELECT exam_venue AS venue 
  FROM application 
 WHERE class_level = 1 
   AND rownumber = 1
 GROUP 
    BY venue 
HAVING COUNT(id) < 20

Answer 1

SELECT exam_venue AS场所FROM应用程序WHERE class_level = 1 AND rownumber = 1 GROUP BY场地HAVING COUNT（id）＆lt; 20 LIMIT 0,1

Answer 2

一种简单的方法可以是以下:::

SELECT TOP 1 exam_venue AS venue, COUNT(id)
FROM application 
WHERE class_level = 1 
GROUP BY venue 
HAVING COUNT(id) < 20