SQL查询从同一表合并两个汇总子集
-
14-10-2019 - |
题
我写了一个data.stackexchange查询以查找 用户每天几个小时发布问题和答案. 。您可以在那里看到SQL。现在的结果看起来像这样:
hour hour questions answers
---- ---- --------- -------
0 0 1 4
null 2 null 4
null 3 null 5
null 4 null 7
null 5 null 11
null 6 null 10
null 7 null 6
null 8 null 1
null 13 null 1
null 14 null 7
null 15 null 8
null 16 null 11
null 17 null 4
null 18 null 10
null 19 null 4
null 20 null 6
null 21 null 7
22 22 1 6
null 23 null 2
如何将查询修改为:
- 将两个小时列合并到一个列中,
- 如果问题/答案是
null
, , 调成0
反而。
第2部分是优先级。
编辑: :这是原始查询的完整SQL,因为我将根据答案进行改进:
SELECT
q.hour, a.hour, questions, answers
FROM
(
SELECT
datepart(hour,creationdate) AS hour,
count(*) AS questions
FROM posts
WHERE posttypeid=1 AND OwnerUserId=##UserID##
GROUP BY datepart(hour,creationdate)
) q
FULL JOIN
(
SELECT
datepart(hour,creationdate) AS hour,
count(*) AS answers
FROM posts
WHERE posttypeid=2 AND OwnerUserId=##UserID##
GROUP BY datepart(hour,creationdate)
) a
ON q.hour = a.hour
ORDER BY a.hour, q.hour
解决方案
SELECT
ISNULL(q.hour, a.hour) AS hour,
ISNULL(questions,0) AS questions,
ISNULL(answers,0) AS answers
或重写查询以摆脱 full join
SELECT
datepart(hour,creationdate) AS hour,
count(CASE WHEN posttypeid = 1 THEN 1 END) AS questions,
count(CASE WHEN posttypeid = 2 THEN 1 END) AS answers
FROM posts
WHERE posttypeid IN (1,2) AND OwnerUserId=##UserID##
GROUP BY datepart(hour,creationdate)
不隶属于 StackOverflow