要获得与亚马逊 Timestream 类似的功能 LiveAnalytics，可以考虑适用于 InfluxDB 的亚马逊 Timestream。适用于 InfluxDB 的 Amazon Timestream 提供简化的数据摄取和个位数毫秒级的查询响应时间，以实现实时分析。点击[此处](https://docs.aws.amazon.com//timestream/latest/developerguide/timestream-for-influxdb.html)了解更多信息。

本文属于机器翻译版本。若本译文内容与英语原文存在差异，则一律以英文原文为准。

# SELECT
<a name="supported-sql-constructs.SELECT"></a>

**SELECT** 语句可用于从一个或多个表中检索数据。Timestream 的查询语言支持以下 **SELECT** 语句的语法：

```
[ WITH with_query [, ...] ]
            SELECT [ ALL | DISTINCT ] select_expr [, ...]
            [ function (expression) OVER (
            [ PARTITION BY partition_expr_list ]
            [ ORDER BY order_list ]
            [ frame_clause ] )
            [ FROM from_item [, ...] ]
            [ WHERE condition ]
            [ GROUP BY [ ALL | DISTINCT ] grouping_element [, ...] ]
            [ HAVING condition]
            [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ]
            [ ORDER BY order_list ]
            [ LIMIT [ count | ALL ] ]
```

where 
+ `function (expression)` 是支持的[窗口函数](window-functions.md)之一。
+ `partition_expr_list` 为：

  ```
  expression | column_name [, expr_list ]
  ```
+ `order_list` 为：

  ```
  expression | column_name [ ASC | DESC ] 
  [ NULLS FIRST | NULLS LAST ]
  [, order_list ]
  ```
+ `frame_clause` 为：

  ```
  ROWS | RANGE
  { UNBOUNDED PRECEDING | expression PRECEDING | CURRENT ROW } |
  {BETWEEN
  { UNBOUNDED PRECEDING | expression { PRECEDING | FOLLOWING } |
  CURRENT ROW}
  AND
  { UNBOUNDED FOLLOWING | expression { PRECEDING | FOLLOWING } |
  CURRENT ROW }}
  ```
+ `from_item` 为以下之一：

  ```
  table_name [ [ AS ] alias [ ( column_alias [, ...] ) ] ]
  from_item join_type from_item [ ON join_condition | USING ( join_column [, ...] ) ]
  ```
+ `join_type` 为以下之一：

  ```
  [ INNER ] JOIN
  LEFT [ OUTER ] JOIN
  RIGHT [ OUTER ] JOIN
  FULL [ OUTER ] JOIN
  ```
+ `grouping_element` 为以下之一：

  ```
  ()
  expression
  ```