avg() over()
时间: 2023-11-16 18:04:19 浏览: 12
The "avg() over()" function is used in SQL to calculate the average value of a column of data over a specified window or partition. The "over()" clause is used to specify the window or partition for the calculation. This function is often used in combination with other window functions to perform complex calculations on data sets. For example, it can be used to calculate the average salary of employees within each department of a company.
相关问题
avg over partition by order by
avg() over(partition by ... order by ...)是一种分析函数,用于计算分组后的平均值。它的具体用法是在partition by子句中指定分组的列,在order by子句中指定排序的列。这样,avg()函数将根据指定的分组和排序条件计算每个分组的平均值。
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avg() over()怎么使用
使用 avg() over() 函数需要遵循以下基本语法:
```
AVG(column) OVER (
[PARTITION BY partition_expression, ... ]
[ORDER BY sort_expression [ASC | DESC], ... ]
)
```
其中:
- `column` 表示要计算平均值的列;
- `PARTITION BY` 子句可选,表示按照哪个或哪些列进行分组计算;
- `ORDER BY` 子句可选,表示按照哪个或哪些列进行排序,如果不指定则默认按照当前行的顺序进行计算。
下面是一个示例,假设有一个名为 `sales` 的表,其中包含 `id`、`name`、`date` 和 `amount` 四个列,我们想要计算每个销售员在每个月份的销售额平均值,可以使用如下 SQL 语句:
```
SELECT id, name, date, amount,
AVG(amount) OVER (PARTITION BY name, EXTRACT(MONTH FROM date)
ORDER BY date) AS avg_amount
FROM sales;
```
在这个示例中,我们使用 `PARTITION BY` 子句对 `name` 和 `date` 列进行分组,其中 `EXTRACT(MONTH FROM date)` 表示从 `date` 列中提取月份,然后按照 `date` 列进行排序,最后在每个分组内计算 `amount` 列的平均值,并将结果命名为 `avg_amount`。
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