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https://issues.apache.org/jira/browse/IOTDB-4592?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17616123#comment-17616123
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Xingyu Liu commented on IOTDB-4592:
-----------------------------------
{{LAST_VALUE}} is an aggregate function. It finds the value with the largest
timestamp and its return contains *NO* timestamp column.
Please note that mixed use of {{Aggregate Query}} and {{Timeseries Query}} is
not allowed.
For more details of aggregate functions, please take a look at
[https://iotdb.apache.org/UserGuide/Master/Query-Data/Aggregate-Query.html]
Here is an example:
{{!image-2022-10-12-09-59-52-239.png!}}
The query results contain no timestamp column. In this case, the return value
of function "GetTimestamp()" is always 0.
For Chinese version:
{{LAST_VALUE}} 是一个聚合查询函数，它能找到有最大时间戳的值，并且返回值中{*}不包含{*}时间戳列。
请注意不要混用聚合查询和时间序列查询，这是不被允许的。
想要了解更多和聚合函数相关的内容，请参考[https://iotdb.apache.org/zh/UserGuide/Master/Query-Data/Aggregate-Query.html|https://iotdb.apache.org/zh/UserGuide/Master/Query-Data/Aggregate-Query.html#%E5%86%85%E7%BD%AE%E8%81%9A%E5%90%88%E5%87%BD%E6%95%B0]
图中是一个查询的示例，可以看到使用了 {{LAST_VALUE}} 的查询结果中不包含时间戳列。此时，函数"GetTimestamp()"的返回值始终为0.
> go client "select last_value()" timestamp get 0
> -----------------------------------------------
>
> Key: IOTDB-4592
> URL: https://issues.apache.org/jira/browse/IOTDB-4592
> Project: Apache IoTDB
> Issue Type: Bug
> Reporter: mxz
> Assignee: Xingyu Liu
> Priority: Major
> Attachments: WechatIMG2.jpeg, image-2022-10-12-09-59-52-239.png
>
>
> go client
> The timestamp obtained through the interface is 0
> !WechatIMG2.jpeg!
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