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Posted to reviews@iotdb.apache.org by GitBox <gi...@apache.org> on 2022/08/14 08:41:52 UTC
[GitHub] [iotdb] jixuan1989 commented on issue #6981: 跨设备查询时的时间排序问题
jixuan1989 commented on issue #6981:
URL: https://github.com/apache/iotdb/issues/6981#issuecomment-1214312517
current `align by device` sql does not support align by device first and then align by time.
But using the default query, you can get the result order by time. However, this kind of query is not friendly for cases which have many devices.
```sql
IoTDB> insert into root.sg1.d1(time, s1) values (1, 2);
Msg: The statement is executed successfully.
IoTDB> insert into root.sg1.d1(time, s1) values (5, 2);
Msg: The statement is executed successfully.
IoTDB> insert into root.sg1.d2(time, s1) values (3, 2);
Msg: The statement is executed successfully.
IoTDB> select * from root.**;
+-----------------------------+--------------+--------------+
| Time|root.sg1.d1.s1|root.sg1.d2.s1|
+-----------------------------+--------------+--------------+
|1970-01-01T08:00:00.001+08:00| 2.0| null|
|1970-01-01T08:00:00.003+08:00| null| 2.0|
|1970-01-01T08:00:00.005+08:00| 2.0| null|
+-----------------------------+--------------+--------------+
Total line number = 3
It costs 0.182s
IoTDB> select * from root.** align by device;
+-----------------------------+-----------+---+
| Time| Device| s1|
+-----------------------------+-----------+---+
|1970-01-01T08:00:00.001+08:00|root.sg1.d1|2.0|
|1970-01-01T08:00:00.005+08:00|root.sg1.d1|2.0|
|1970-01-01T08:00:00.003+08:00|root.sg1.d2|2.0|
+-----------------------------+-----------+---+
Total line number = 3
It costs 0.047s
```
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