From c1b518722bffe6cd8ad998d16d8199bbc21a4f75 Mon Sep 17 00:00:00 2001 From: Xiaoyu Wang Date: Sat, 17 Sep 2022 13:41:51 +0800 Subject: [PATCH] docs: fix query doc error --- docs/en/12-taos-sql/12-distinguished.md | 10 ++++++++-- docs/zh/12-taos-sql/12-distinguished.md | 10 ++++++++-- 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/docs/en/12-taos-sql/12-distinguished.md b/docs/en/12-taos-sql/12-distinguished.md index 98b782c3eb..296c237642 100644 --- a/docs/en/12-taos-sql/12-distinguished.md +++ b/docs/en/12-taos-sql/12-distinguished.md @@ -46,7 +46,7 @@ The following restrictions apply: ### Other Rules -- The window clause must occur after the PARTITION BY clause and before the GROUP BY clause. It cannot be used with a GROUP BY clause. +- The window clause must occur after the PARTITION BY clause. It cannot be used with a GROUP BY clause. - SELECT clauses on windows can contain only the following expressions: - Constants - Aggregate functions @@ -78,7 +78,7 @@ These pseudocolumns occur after the aggregation clause. 1. A huge volume of interpolation output may be returned using `FILL`, so it's recommended to specify the time range when using `FILL`. The maximum number of interpolation values that can be returned in a single query is 10,000,000. 2. The result set is in ascending order of timestamp when you aggregate by time window. -3. If aggregate by window is used on STable, the aggregate function is performed on all the rows matching the filter conditions. If `PARTITION BY` is not used in the query, the result set will be returned in strict ascending order of timestamp; otherwise the result set is not exactly in the order of ascending timestamp in each group. +3. If aggregate by window is used on STable, the aggregate function is performed on all the rows matching the filter conditions. If `PARTITION BY` is not used in the query, the result set will be returned in strict ascending order of timestamp; otherwise the result set will be returned in the order of ascending timestamp in each group. ::: @@ -120,6 +120,12 @@ In case of using integer, bool, or string to represent the status of a device at SELECT COUNT(*), FIRST(ts), status FROM temp_tb_1 STATE_WINDOW(status); ``` +Only care about the information of the status window when the status is 2. For example: + +``` +SELECT * FROM (SELECT COUNT(*) AS cnt, FIRST(ts) AS fst, status FROM temp_tb_1 STATE_WINDOW(status)) t WHERE status = 2; +``` + ### Session Window The primary key, i.e. timestamp, is used to determine which session window a row belongs to. As shown in the figure below, if the limit of time interval for the session window is specified as 12 seconds, then the 6 rows in the figure constitutes 2 time windows, [2019-04-28 14:22:10，2019-04-28 14:22:30] and [2019-04-28 14:23:10，2019-04-28 14:23:30] because the time difference between 2019-04-28 14:22:30 and 2019-04-28 14:23:10 is 40 seconds, which exceeds the time interval limit of 12 seconds. diff --git a/docs/zh/12-taos-sql/12-distinguished.md b/docs/zh/12-taos-sql/12-distinguished.md index 268712e757..861ef4ebb7 100644 --- a/docs/zh/12-taos-sql/12-distinguished.md +++ b/docs/zh/12-taos-sql/12-distinguished.md @@ -46,7 +46,7 @@ SELECT select_list FROM tb_name ### 窗口子句的规则 -- 窗口子句位于数据切分子句之后，GROUP BY 子句之前，且不可以和 GROUP BY 子句一起使用。 +- 窗口子句位于数据切分子句之后，不可以和 GROUP BY 子句一起使用。 - 窗口子句将数据按窗口进行切分，对每个窗口进行 SELECT 列表中的表达式的计算，SELECT 列表中的表达式只能包含： - 常量。 - _wstart伪列、_wend伪列和_wduration伪列。 @@ -71,7 +71,7 @@ FILL 语句指定某一窗口区间数据缺失的情况下的填充模式。填 1. 使用 FILL 语句的时候可能生成大量的填充输出，务必指定查询的时间区间。针对每次查询，系统可返回不超过 1 千万条具有插值的结果。 2. 在时间维度聚合中，返回的结果中时间序列严格单调递增。 -3. 如果查询对象是超级表，则聚合函数会作用于该超级表下满足值过滤条件的所有表的数据。如果查询中没有使用 PARTITION BY 语句，则返回的结果按照时间序列严格单调递增；如果查询中使用了 PARTITION BY 语句分组，则返回结果中每个 PARTITION 内不按照时间序列严格单调递增。 +3. 如果查询对象是超级表，则聚合函数会作用于该超级表下满足值过滤条件的所有表的数据。如果查询中没有使用 PARTITION BY 语句，则返回的结果按照时间序列严格单调递增；如果查询中使用了 PARTITION BY 语句分组，则返回结果中每个 PARTITION 内按照时间序列严格单调递增。 ::: @@ -113,6 +113,12 @@ SELECT COUNT(*) FROM temp_tb_1 INTERVAL(1m) SLIDING(2m); SELECT COUNT(*), FIRST(ts), status FROM temp_tb_1 STATE_WINDOW(status); ``` +仅关心 status 为 2 时的状态窗口的信息。例如： + +``` +SELECT * FROM (SELECT COUNT(*) AS cnt, FIRST(ts) AS fst, status FROM temp_tb_1 STATE_WINDOW(status)) t WHERE status = 2; +``` + ### 会话窗口 会话窗口根据记录的时间戳主键的值来确定是否属于同一个会话。如下图所示，如果设置时间戳的连续的间隔小于等于 12 秒，则以下 6 条记录构成 2 个会话窗口，分别是：[2019-04-28 14:22:10，2019-04-28 14:22:30]和[2019-04-28 14:23:10，2019-04-28 14:23:30]。因为 2019-04-28 14:22:30 与 2019-04-28 14:23:10 之间的时间间隔是 40 秒，超过了连续时间间隔（12 秒）。 -- GitLab