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Copy file name to clipboardExpand all lines: src/UserGuide/Master/Table/User-Manual/Tree-to-Table_timecho.md
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@@ -141,7 +141,7 @@ AS root.db.**
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### 2.2 Modifying a Table View
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#### 2.2.1 Syntax Definition
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The ALTER VIEW function supports modifying the view name, adding columns, renaming columns, deleting columns, setting the view's TTL property, and adding comments via COMMENT.
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The ALTER VIEW function supports modifying the view name, adding columns, renaming columns, modifying FIELD column data type (supported since V2.0.8), deleting columns, setting the view's TTL property, and adding comments via COMMENT.
ALTERVIEW [IF EXISTS] viewName ALTER COLUMN [IF EXISTS] columnName SET DATA TYPE new_type
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-- Delete a column from the view
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ALTERVIEW [IF EXISTS] viewName DROP COLUMN [IF EXISTS] columnName
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1. The `SET PROPERTIES`operation currently only supports configuring the TTL property for the table view.
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2. The `DROP COLUMN`function only supports deleting FIELD columns; TAG columns cannot be deleted.
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3. Modifying the comment will overwrite the original comment. If set to `null`, the previous comment will be erased.
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4. When modifying the data type of a FIELD column, the new data type must be compatible with the original type. The specific compatibility is shown in the following table:
* SHOW LATEST? TIMESERIES pathPattern? whereClause? limitClause?
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It is worth noting that when the queried path does not exist, the system will return no timeseries.
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### 2.5 Count Timeseries
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### 2.6 Count Timeseries
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IoTDB is able to use `COUNT TIMESERIES <Path>` to count the number of timeseries matching the path. SQL statements are as follows:
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> Note: The path of timeseries is just a filter condition, which has no relationship with the definition of level.
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### 2.6 Active Timeseries Query
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### 2.7 Active Timeseries Query
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By adding WHERE time filter conditions to the existing SHOW/COUNT TIMESERIES, we can obtain time series with data within the specified time range.
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It is important to note that in metadata queries with time filters, views are not considered; only the time series actually stored in the TsFile are taken into account.
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```
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Regarding the definition of active time series, data that can be queried normally is considered active, meaning time series that have been inserted but deleted are not included.
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### 2.7 Tag and Attribute Management
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### 2.8 Tag and Attribute Management
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We can also add an alias, extra tag and attribute information while creating one timeseries.
Copy file name to clipboardExpand all lines: src/UserGuide/latest-Table/User-Manual/Tree-to-Table_timecho.md
+22-1Lines changed: 22 additions & 1 deletion
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Original file line number
Diff line number
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@@ -141,7 +141,7 @@ AS root.db.**
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### 2.2 Modifying a Table View
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#### 2.2.1 Syntax Definition
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-
The ALTER VIEW function supports modifying the view name, adding columns, renaming columns, deleting columns, setting the view's TTL property, and adding comments via COMMENT.
144
+
The ALTER VIEW function supports modifying the view name, adding columns, renaming columns, modifying FIELD column data type (supported since V2.0.8), deleting columns, setting the view's TTL property, and adding comments via COMMENT.
ALTERVIEW [IF EXISTS] viewName ALTER COLUMN [IF EXISTS] columnName SET DATA TYPE new_type
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-- Delete a column from the view
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ALTERVIEW [IF EXISTS] viewName DROP COLUMN [IF EXISTS] columnName
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@@ -171,6 +174,21 @@ COMMENT ON COLUMN qualifiedName '.' column=identifier IS (string | NULL) #commen
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1. The `SET PROPERTIES`operation currently only supports configuring the TTL property for the table view.
172
175
2. The `DROP COLUMN`function only supports deleting FIELD columns; TAG columns cannot be deleted.
173
176
3. Modifying the comment will overwrite the original comment. If set to `null`, the previous comment will be erased.
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4. When modifying the data type of a FIELD column, the new data type must be compatible with the original type. The specific compatibility is shown in the following table:
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