块引用
鉴于这些要求：
速率查找表：
effective_start_date | effective_end_date | amount | rate_type
----------------------------------------------------------------
2016-01-16 00:00:00 | 2016-02-15 00:00:00 | 0.10 | rate1
2016-01-16 00:00:00 | 2016-02-15 00:00:00 | 156 | rate2 (annual)
2016-02-16 00:00:00 | 2016-03-15 00:00:00 | 0.15 | rate1
输入/源表：
datetime | person | qty | x | vatable
-------------------------------------------------
2016-01-15 00:00:00 | p1 | 10 | x1 | Y
2016-01-16 00:00:00 | p1 | 10 | x1 | Y
2016-01-16 00:00:00 | p1 | 11 | x2 | N
2016-01-16 01:00:00 | p1 | 9 | x1 | Y
2016-01-16 02:00:00 | p2 | 10 | x1 | Y
2016-02-15 00:00:00 | p1 | 8 | x1 | Y
2016-02-15 00:00:00 | p1 | 8 | x2 | Y
2016-02-16 00:00:00 | p1 | 8 | x1 | Y
2016-02-16 00:00:00 | p1 | 7 | x2 | Y
如果使用rate2：
每月数量=参数每月数量之和（1月16日-31日，2月1日-15日）
计算单价=单价金额/12/月单价
计算费用=计算费率*数量
增值税数量=增值税数量之和=Y
增值税=计算税率*可增值数量*0.12
如果param=1月16日-2月15日（期间以有效开始和结束日期为界）
需要输出表：
datetime | person | qty | monthly_qty | calc_rate | calc_fee | vat_qty | vat
--------------------------------------------------------------------------------------------------
2016-01-16 00:00:00 | p1 | 21 | 40 | 156/12/40 | calc_rate * 21 | 10 | calc_rate * 10 * 0.12
2016-01-16 01:00:00 | p1 | 9 | 40 | 156/12/40 | calc_rate * 9 | 9 | calc_rate * 9 * 0.12
2016-01-16 02:00:00 | p2 | 10 | 40 | 156/12/40 | calc_rate * 10 | 10 | calc_rate * 10 * 0.12
2016-02-15 00:00:00 | p1 | 16 | 16 | 156/12/16 | calc_rate * 16 | 16 | calc_rate * 16 * 0.12
（1）我弄错了
total_qty_per_month（每月数量）-1月份，总共包括2016-01-15，实际：50，预期：40（仅10+11+9+10）编辑：这是我更新的SQL:（我正在使用一个视图）
select it.datetime, it.person, 'rate2'::varchar as rate_used,
sum(it.qty) as qty,
rl.amount, rl.effective_start_date, rl.effective_end_date,
sum(sum(it.qty)) over w_month as total_qty_per_month,
rl.amount / 12 / sum(sum(it.qty)) over w_month as calculated_rate,
((rl.amount / 12 / sum(sum(it.qty)) over w_month) * sum(qty)) as calculated_fee,
sum(case when it.vatable = 'Y' then it.qty else 0 end) as vatable_qty
from input_table it
inner join rate_lookup_table rl on it.datetime between rl.effective_start_date and rl.effective_end_date
where it.person_type='PT1' and rl.rate_type = 'rate2'
group by it.datetime, it.person, rl.amount, rl.effective_start_date, rl.effective_end_date
window w_month as (partition by date_trunc('month', it.datetime))
order by it.datetime
我需要得到基于
effective_start_date和effective_end_date的窗口函数的和。 最佳答案
据我所知，您可以使用join withbetween和awindow function来计算每月的总和：
select it.datetime, it.person, it.qty, rl.amount, rl.rate_type,
rl.amount / 12 / sum(it.qty) over (partition by date_trunc('month', it.datetime)) as calculated_rate
from rate_lookup_table rl
join input_table it on it.datetime between rl.effective_start_date and effective_end_date
where rl.rate_type = 'rate2';
date_trunc('month', it.datetime)“normalized”到月初的日期，因此同一个月的所有值都相同。因此窗口函数将汇总同一个月的所有数量。根据您的样本数据，这将返回：
datetime | person | qty | amount | rate_type | calculated_rate
--------------------+--------+-----+--------+-----------+----------------
2016-01-16 00:00:00 | p1 | 10 | 156 | rate2 | 0.45
2016-01-16 01:00:00 | p1 | 9 | 156 | rate2 | 0.45
2016-01-16 02:00:00 | p2 | 10 | 156 | rate2 | 0.45
2016-02-15 00:00:00 | p1 | 8 | 156 | rate2 | 1.63
计算出的费用和增值税可以从计算出的税率中得出。要不重复表达式，可以使用派生表：
select *,
calculated_rate * qty as calculated_fee,
calculated_rate * qty * 0.12 as vat
from (
select it.datetime, it.person, it.qty, rl.amount, rl.rate_type,
rl.amount / 12 / sum(it.qty) over (partition by date_trunc('month', it.datetime)) as calculated_rate
from rate_lookup_table rl
join input_table it on it.datetime between rl.effective_start_date and effective_end_date
where rl.rate_type = 'rate2'
) t;