Oracle-分析函数（累计求和，排序等）

在Oracle数据库中，可以使用分析函数(Analytic Functions)来进行如累计求和、排名等操作。以下是一些使用这些函数的例子：

1. 累计求和(SUM)：

SELECT 
    column_name,
    SUM(column_name) OVER (ORDER BY some_column) AS cumulative_sum
FROM 
    table_name;

2. 排名(RANK)：

SELECT 
    column_name,
    RANK() OVER (ORDER BY column_name DESC) AS rank
FROM 
    table_name;

3. 分区求和(PARTITION BY)：

SELECT 
    partition_column,
    column_to_sum,
    SUM(column_to_sum) OVER (PARTITION BY partition_column) AS partition_sum
FROM 
    table_name;

4. 窗口函数(ROW\_NUMBER, DENSE\_RANK, RAT\_RANK)：

SELECT 
    column_name,
    ROW_NUMBER() OVER (ORDER BY column_name) AS row_num,
    DENSE_RANK() OVER (ORDER BY column_name) AS dense_rank,
    RAT_RANK() OVER (ORDER BY column_name) AS rank
FROM 
    table_name;

5. 前后行访问(LAG, LEAD)：

SELECT 
    column_name,
    LAG(column_name) OVER (ORDER BY column_name) AS previous_value,
    LEAD(column_name) OVER (ORDER BY column_name) AS next_value
FROM 
    table_name;

6. 窗口大小控制(ROWS BETWEEN)：

SELECT 
    column_name,
    SUM(column_name) OVER (
        ORDER BY some_column
        ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
    ) AS cumulative_sum
FROM 
    table_name;

这些分析函数可以提供强大的数据分析能力，并且能够在查询时直接进行复杂的操作，而不需要额外的子查询或者是数据处理逻辑。