xxq250
/
homework-jianmu
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Wiki Activity

Update 14-stream.md

This commit is contained in:
liuyao 2024-03-01 15:09:57 +08:00 committed by GitHub
parent 98fa384da2
commit e20dc784f8
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 4 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
docs/en/12-taos-sql/14-stream.md
View File

@ -41,10 +41,14 @@ window_clause: {
SESSION(ts_col, tol_val)
| STATE_WINDOW(col)
| INTERVAL(interval_val [, interval_offset]) [SLIDING (sliding_val)]
| EVENT_WINDOW START WITH start_trigger_condition END WITH end_trigger_condition
| COUNT_WINDOW(count_val[, sliding_val])
}
```
`SESSION` indicates a session window, and `tol_val` indicates the maximum range of the time interval. If the time interval between two continuous rows are within the time interval specified by `tol_val` they belong to the same session window; otherwise a new session window is started automatically.
COUNT_WINDOW is a counting window that is divided by a fixed number of data rows.count_val: A constant, which is a positive integer and must be greater than or equal to 2. The maximum value is 2147483648. count_val represents the maximum number of data rows contained in each COUNT_WINDOW.
When the total number of data rows cannot be divided by count_val, the number of rows in the last window will be less than count_val. sliding_val: is a constant that represents the number of window slides, similar to SLIDING in intervals
For example, the following SQL statement creates a stream and automatically creates a supertable named `avg_vol`. The stream has a 1 minute time window that slides forward in 30 second intervals to calculate the average voltage of the meters supertable.