sql - SQL标准中的最大和最小

我的理解是GREATEST（）和LEAST（）并不是SQL标准的一部分，但是很常见。

我想知道，是否有一种方法可以在SQL标准内克隆GREATEST的功能？

SELECT id, GREATEST(1,2,3,4,5,6,7) AS number FROM table

完整查询：

  SELECT SUBSTR(section,1,2) AS campus,
           AVG(GREATEST(maximum - enrolled, 0)) AS empty
    FROM sectionrun
   WHERE coursenumber = '105' AND subject = 'ENGL'
GROUP BY campus

最佳答案

您可以使用CASE表达式：

  SELECT SUBSTR(section,1,2) AS campus,
           AVG(CASE WHEN maximum - enrolled > 0
                    THEN maximum - enrolled
                    ELSE 0
               END) AS empty
    FROM sectionrun
   WHERE coursenumber = '105' AND subject = 'ENGL'
GROUP BY campus