Question

如果特定item_id存在两个或更多非零值，我只想计算值的AVG。如果不存在两个或多个非零值，我不想计算AVG。

当前的SQL如下。也许首先应该有一个if子句？......任何想法？

SELECT AVG( days_since ) AS days_out
  FROM (
    SELECT days_since
    FROM user_123
    WHERE item_id = 645
AND days_since <> 0
ORDER BY id DESC
    LIMIT 5
  ) AS recent

似乎可以使用If子句;

IF SELECT COUNT (*), item_id, days_since >= 2 
where days_since <>0, then perform AVG...

Answer 1

怎么样：

SELECT AVG(days_since) AS days_out
  FROM User_123
 WHERE Item_ID = 645
   AND Days_Since <> 0
HAVING COUNT(*) > 1

我不确定ORDER BY和LIMIT条款的用途，因此您必须调整答案以重新表达它们所隐含的条件。

如何在重新应用Order By和Limit时保持其正常工作。使用它们以便在平均值计算中仅使用最近的5个条目。

SELECT AVG(days_since) AS days_out
  FROM (SELECT days_since
          FROM User_123
         WHERE Item_ID = 645
           AND Days_Since <> 0
         ORDER BY ID DESC
         LIMIT 5
       ) AS u
HAVING COUNT(*) > 1;

仅当多于一个值（不等于0）退出时，SQL查询才能平均值？

1 个答案: