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Update 12-distinguished.md

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docs/en/12-taos-sql/12-distinguished.md
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@ -38,20 +38,15 @@ Aggregation by time window is supported in TDengine. For example, in the case wh
window_clause: {
SESSION(ts_col, tol_val)
| STATE_WINDOW(col)
| INTERVAL(interval [, offset]) [SLIDING (interval)] [FILL({NONE | VALUE | PREV | NULL | LINEAR | NEXT})]
| INTERVAL(interval_val [, offset]) [SLIDING (sliding_value)] [FILL({NONE | VALUE | PREV | NULL | LINEAR | NEXT})]
| EVENT_WINDOW START WITH start_trigger_condition END WITH end_trigger_condition
}
interval:
TK_NUMBER
| TK_STRING
| TK_DURATION
```
The parameters of INTERVAL(`interval` or `offset`) and SLIDING are time durations which have 3 forms of representation.
- `INTERVAL(1s, 500a) SLIDING(1s)`, the unit char should be one of `a (millisecond), b (nanosecond), d (day), h (hour), m (minute), n (month), s (second), u (microsecond), w (week), y (year)`.
- `INTERVAL(1000, 500) SLIDING(1000)`, the unit will the same as the database.
- `INTERVAL('1s', '500a') SLIDING('1s')`, or double quoted. Unit must be specified, no spaces allowed.
Both interval_val and sliding_value are time durations which have 3 forms of representation.
- INTERVAL(1s, 500a) SLIDING(1s), the unit char should be any one of a (millisecond), b (nanosecond), d (day), h (hour), m (minute), n (month), s (second), u (microsecond), w (week), y (year).
- INTERVAL(1000, 500) SLIDING(1000), the unit will the same as the queried database, if there are more than one databases, higher precision will be used.
- INTERVAL('1s', '500a') SLIDING('1s'), unit must be specified, no spaces allowed.
The following restrictions apply: