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Update 14-stream.md

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@ -47,8 +47,12 @@ window_clause: {
```
`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
`EVENT_WINDOW` is determined according to the window start condition and the window close condition. The window is started when `start_trigger_condition` is evaluated to true, the window is closed when `end_trigger_condition` is evaluated to true. `start_trigger_condition` and `end_trigger_condition`
can be any conditional expressions supported by TDengine and can include multiple columns.
`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 `INTERVAL`.
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.