我正在寻找查询应用程序消息输出的帮助。我有一个查询,它获取每条消息的行并将它们连接在一起以形成一个句子。然而,我的一些消息号码有两条或更多条消息,在这种情况下,我只想要最新日期的消息。我当前的代码通过将每个消息编号的行号连接在一起并按 MSG_NUM 的顺序输出它们来输出一个句子中的所有消息。我已经在 MSG_START_DATE 添加了排序,但正如预期的那样,这仍然给了我两个。如何为每个连接的消息行选择最大值?
以下是我正在使用的字段:
MSG_NUM | MSG_START_DATE | MSG_LINE_NUM | MSG_TEXT
1 | 2010-01-15 | 1 | Invalid operation
1 | 2010-01-15 | 2 | try again
1 | 2014-02-21 | 1 | Invalid input
1 | 2014-02-21 | 2 | try again
这是我当前的代码:
Select distinct ST2.[MSG_NUM],
substring(
(
(Select ' '+LTRIM(RTRIM(ST1.[MSG_TEXT])) AS [text()]
From database..messages ST1
Where ST1.[MSG_NUM] = ST2.[MSG_NUM]
ORDER BY ST1.[MSG_START_DATE], ST1.[MSG_LINE_NUM]
For XML PATH (''),root('xmlchar'), type).value('/xmlchar[1]','varchar(max)')
), 2, 2000) [Message]
From database..messages ST2 order by ST2.[MSG_NUM]
这是我收到的输出:
1 Invalid operation try again Invalid input try again
我只想要输出:
1 Invalid input try again
关于我如何做到这一点的任何想法?
最佳答案
你按日期过滤呢?
Select distinct ST2.[MSG_NUM],
substring(
(
(Select ' '+LTRIM(RTRIM(ST1.[MSG_LINE_NUM])) AS [text()]
From database..messages ST1
Where ST1.[MSG_NUM] = ST2.[MSG_NUM]
AND ST1.[MSG_START_DATE] = (SELECT MAX(ST3.[MSG_START_DATE])
FROM database..messages ST3
WHERE ST2.[MSG_NUM] = ST3.[MSG_NUM]
)
ORDER BY ST1.[MSG_LINE_NUM]
For XML PATH (''),root('xmlchar'), type).value('/xmlchar[1]','varchar(max)')
), 2, 2000) [Message]
From database..messages ST2 order by ST2.[MSG_NUM]
更好的是,在传递给您的查询之前进行过滤
WITH maxd
AS (
SELECT *
,MAX(MSG_START_DATE) OVER (PARTITION BY [MSG_NUM]) AS maxdate
FROM DATABASE..messages
)
,filter
AS (
SELECT *
FROM maxd
WHERE MSG_START_DATE = maxdate
)
SELECT DISTINCT ST2.[MSG_NUM]
,substring((
(
SELECT ' ' + LTRIM(RTRIM(ST1.[MSG_LINE_NUM])) AS [text()]
FROM filter ST1
WHERE ST1.[MSG_NUM] = ST2.[MSG_NUM]
ORDER BY ST1.[MSG_LINE_NUM]
FOR XML PATH('')
,root('xmlchar')
,type
).value('/xmlchar[1]', 'varchar(max)')
), 2, 2000) [Message]
FROM filter ST2
ORDER BY ST2.[MSG_NUM]
关于具有相同 ID 和最新日期的 SQL 连接行,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33838550/