PLSQL 查询语句：统计每月所有企业所有税种的税额累计总额

可以使用子查询和窗口函数来实现：

SELECT month, corp, tax_type, SUM(tax_amount) AS total_tax_amount
FROM (
  SELECT month, corp, tax_type,
    COALESCE(tax_amount, LAST_VALUE(tax_amount IGNORE NULLS) OVER (PARTITION BY corp, tax_type ORDER BY month ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)) AS tax_amount
  FROM nsxx
  WHERE EXTRACT(YEAR FROM month) = 2022
)
GROUP BY month, corp, tax_type
ORDER BY month, corp, tax_type

首先，使用子查询筛选出 2022 年的数据，并使用窗口函数中的LAST_VALUE函数来取离当前行最近的非空值。然后，将结果按月、企业、税种分组，并计算每组的tax_amount总和。最后，按月、企业、税种排序输出结果。