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commit 47cafef4fdbe0bce0f818a7839500ca261f5a059 Author: Minghui Liu <[email protected]> AuthorDate: Wed Nov 2 16:40:27 2022 +0800 update Select-Expression --- docs/UserGuide/Query-Data/Select-Expression.md | 14 -------------- docs/zh/UserGuide/Query-Data/Select-Expression.md | 14 -------------- 2 files changed, 28 deletions(-) diff --git a/docs/UserGuide/Query-Data/Select-Expression.md b/docs/UserGuide/Query-Data/Select-Expression.md index 8df849d69e..8241b38762 100644 --- a/docs/UserGuide/Query-Data/Select-Expression.md +++ b/docs/UserGuide/Query-Data/Select-Expression.md @@ -1293,20 +1293,6 @@ It costs 0.012s - Only when the left operand and the right operand under a certain timestamp are not `null`, the nested expressions will have an output value. Otherwise this row will not be included in the result. But for nested expressions with `GROUP BY` clause, it is better to show the result of all time intervals. Please refer to Input3 and corresponding Result3 in Example. - If one operand in the nested expressions can be translated into multiple time series (For example, `*`), the result of each time series will be included in the result (Cartesian product). Please refer to Input2 and corresponding Result2 in Example. -##### Note - -> Automated fill (`FILL`) and grouped by level (`GROUP BY LEVEL`) are not supported in an aggregation query with expression nested. They may be supported in future versions. -> -> The aggregation expression must be the lowest level input of one expression tree. Any kind expressions except timeseries are not valid as aggregation function parameters。 -> -> In a word, the following queries are not valid. -> -> ```sql -> SELECT avg(s1+1) FROM root.sg.d1; -- The aggregation function has expression parameters. -> SELECT avg(s1) + avg(s2) FROM root.sg.* GROUP BY LEVEL=1; -- Grouped by level -> SELECT avg(s1) + avg(s2) FROM root.sg.d1 GROUP BY([0, 10000), 1s) FILL(previous); -- Automated fill -> ``` - ## Use Alias Since the unique data model of IoTDB, lots of additional information like device will be carried before each sensor. Sometimes, we want to query just one specific device, then these prefix information show frequently will be redundant in this situation, influencing the analysis of result set. At this time, we can use `AS` function provided by IoTDB, assign an alias to time series selected in query. diff --git a/docs/zh/UserGuide/Query-Data/Select-Expression.md b/docs/zh/UserGuide/Query-Data/Select-Expression.md index 2db8fc662d..9939b22156 100644 --- a/docs/zh/UserGuide/Query-Data/Select-Expression.md +++ b/docs/zh/UserGuide/Query-Data/Select-Expression.md @@ -1293,20 +1293,6 @@ It costs 0.012s - 当某个时间戳下左操作数和右操作数都不为空（`null`）时，表达式才会有结果，否则表达式值为`null`，且默认不出现在结果集中。但在使用`GROUP BY`子句的聚合查询嵌套表达式中，我们希望保留每个时间窗口的值，所以表达式值为`null`的窗口也包含在结果集中。请参考输入3及结果集3。 - 如果表达式中某个操作数对应多条时间序列（如通配符`*`），那么每条时间序列对应的结果都会出现在结果集中（按照笛卡尔积形式）。请参考输入2及结果集2。 -#### 注意 - -> 目前此功能尚不支持填充算子（`FILL`）和按层级聚合（`GROUP BY LEVEL`）查询, 在后续版本会支持。 -> -> 聚合计算目前只能当做最底层表达式输入，暂不支持聚合函数内部出现表达式。 -> -> 即不支持以下查询 -> -> ```SQL -> SELECT avg(s1 + 1) FROM root.sg.d1; -- 聚合函数内部有表达式 -> SELECT avg(s1) + avg(s2) FROM root.sg.* GROUP BY LEVEL=1; -- 按层级聚合 -> SELECT avg(s1) + avg(s2) FROM root.sg.d1 GROUP BY([0, 10000), 1s) FILL(previous); -- 空值填充 -> ``` - ## 使用别名 由于 IoTDB 独特的数据模型，在每个传感器前都附带有设备等诸多额外信息。有时，我们只针对某个具体设备查询，而这些前缀信息频繁显示造成了冗余，影响了结果集的显示与分析。这时我们可以使用 IoTDB 提供的 AS 函数，将查询中出现的时间序列给定一个别名。
