postgres子查询中列的动态生成

Question

下面的查询给出了特定年份的名称、ID、订阅、打开、关闭、总金额的详细信息，即，posted_date 是查询的输入。

select la.name,la.id,la.parent_id,la.is_group,tb1.opening op_1,tb1.closing cl_1,
coalesce((select sum(j.amount) from journal j,voucher v , ledger_account le where j.voucher_id=v.id and le.id=j.ledger_account_id and la.id=le.id and
 v.posted_date::date>='2020-04-01' and v.posted_date::date<='2021-03-31'),0) balance_2020
from ledger_account la left join trialb tb1 on tb1.ledger_account_id=la.id and tb1.fy_id=1

上面的查询给出了 2020 年的总数据和余额，例如：-如果我需要 2005 年的余额，我再次需要多次粘贴以下逻辑

coalesce((select sum(j.amount) from journal j,voucher v , ledger_account le where j.voucher_id=v.id and le.id=j.ledger_account_id and la.id=le.id and  v.posted_date::date>='2020-04-01' and v.posted_date::date<='2021-03-31'),0) balance_2020

并将 v.posted 日期和列名更改为
v.posted_date::date>='2005-04-01' 和 v.posted_date::date<='2006-03-31'),0) balance_2005等近 15 次以获得到 2020 年的总余额查询的大小每年都在增加，过程所花费的时间。

那么是否有任何替代或可能的方法可以根据给定查询的输入在必要时动态生成列 balance_2005、balance_2006.. 等等？

Answer 1

将子查询移动到 from 子句并使用条件聚合来获取各种总和：

select
  la.name,
  la.id,
  la.parent_id,
  la.is_group,
  tb1.opening op_1,
  tb1.closing cl_1,
  sums.balance_2018,
  sums.balance_2019,
  sums.balance_2020
from ledger_account la
left join trialb tb1 on tb1.ledger_account_id = la.id and tb1.fy_id = 1
left join
(
  select
    j.ledger_account_id,
    sum(case when v.posted_date::date >= date '2018-04-01' and v.posted_date::date <= date '2019-03-31') then j.amount else 0 end) as balance_2018,
    sum(case when v.posted_date::date >= date '2019-04-01' and v.posted_date::date <= date '2020-03-31') then j.amount else 0 end) as balance_2019,
    sum(case when v.posted_date::date >= date '2020-04-01' and v.posted_date::date <= date '2021-03-31') then j.amount else 0 end) as balance_2020
  from journal j
  join voucher v on v.id = j.voucher_id
  group by j.ledger_account_id
) sums on sums.ledger_account_id = la.id
order by la.name;

如果您不想要固定年份，则不能使用列，而必须使用行。 您需要计算从日期到财政年度，但这只是从中减去三个月。

select
  la.name,
  la.id,
  la.parent_id,
  la.is_group,
  tb1.opening op_1,
  tb1.closing cl_1,
  sums.fiscal_year
  sums.balance
from ledger_account la
left join trialb tb1 on tb1.ledger_account_id = la.id and tb1.fy_id = 1
left join
(
  select
    j.ledger_account_id,
    extract(year from v.posted_date - interval '3 months') as fiscal_year
    sum(j.amount) as balance
  from journal j
  join voucher v on v.id = j.voucher_id
  group by j.ledger_account_id, extract(year from v.posted_date - interval '3 months')
) sums on sums.ledger_account_id = la.id
order by la.name, sums.fiscal_year;

让您的应用循环处理帐户的年度数据。

如果您想避免获得非常大的结果集并将其限制在某些年份，您可以添加此标准，例如

  ...
  where extract(year from v.posted_date - interval '3 months') between 2010 and 2020
  group by j.ledger_account_id, extract(year from v.posted_date - interval '3 months')
  ...