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| # Overview |
| |
| ## 1. Syntax Overview |
| |
| ```SQL |
| SELECT ⟨select_list⟩ |
| FROM ⟨tables⟩ |
| [WHERE ⟨condition⟩] |
| [GROUP BY ⟨groups⟩] |
| [HAVING ⟨group_filter⟩] |
| [FILL ⟨fill_methods⟩] |
| [ORDER BY ⟨order_expression⟩] |
| [OFFSET ⟨n⟩] |
| [LIMIT ⟨n⟩]; |
| ``` |
| |
| The IoTDB table model query syntax supports the following clauses: |
| |
| - **SELECT Clause**: Specifies the columns to be included in the result. Details: [SELECT Clause](../SQL-Manual/Select-Clause.md) |
| - **FROM Clause**: Indicates the data source for the query, which can be a single table, multiple tables joined using the `JOIN` clause, or a subquery. Details: [FROM & JOIN Clause](../SQL-Manual/From-Join-Clause.md) |
| - **WHERE Clause**: Filters rows based on specific conditions. Logically executed immediately after the `FROM` clause. Details: [WHERE Clause](../SQL-Manual/Where-Clause.md) |
| - **GROUP BY Clause**: Used for aggregating data, specifying the columns for grouping. Details: [GROUP BY Clause](../SQL-Manual/GroupBy-Clause.md) |
| - **HAVING Clause**: Applied after the `GROUP BY` clause to filter grouped data, similar to `WHERE` but operates after grouping. Details:[HAVING Clause](../SQL-Manual/Having-Clause.md) |
| - **FILL Clause**: Handles missing values in query results by specifying fill methods (e.g., previous non-null value or linear interpolation) for better visualization and analysis. Details:[FILL Clause](../SQL-Manual/Fill-Clause.md) |
| - **ORDER BY Clause**: Sorts query results in ascending (`ASC`) or descending (`DESC`) order, with optional handling for null values (`NULLS FIRST` or `NULLS LAST`). Details: [ORDER BY Clause](../SQL-Manual/OrderBy-Clause.md) |
| - **OFFSET Clause**: Specifies the starting position for the query result, skipping the first `OFFSET` rows. Often used with the `LIMIT` clause. Details: [LIMIT and OFFSET Clause](../SQL-Manual/Limit-Offset-Clause.md) |
| - **LIMIT Clause**: Limits the number of rows in the query result. Typically used in conjunction with the `OFFSET` clause for pagination. Details: [LIMIT and OFFSET Clause](../SQL-Manual/Limit-Offset-Clause.md) |
| |
| ## 2. Clause Execution Order |
| |
|  |
