[英]Dynamic Date Table
I am creating a Data Model in PowerPivot and am wondering if there is anyway I can create a dynamic date table in SQL. 我正在PowerPivot中创建数据模型,并且想知道是否仍然可以在SQL中创建动态日期表。 I was able to create one in PowerQuery however there are some bugs in PowerQuery(read only connection) when a table is modified in PowerPivot. 我可以在PowerQuery中创建一个表,但是在PowerPivot中修改表时,PowerQuery(只读连接)中存在一些错误。 What I am looking for is to have a start date of 1/1/2013 (interval is days) and as each new year rolls around rows are added to the date table. 我正在寻找的是一个开始日期为2013年1月1日(间隔为天),并且随着每个新年滚动,行都将添加到日期表中。 Is there anyway to do this? 反正有这样做吗?
I am running Postgres 我正在运行Postgres
So far I came up with this, 到目前为止,我想到了这个,
SELECT * FROM dbo.fof_GetDates('1/1/2013', GETDATE())
But I want it to display all dates till end of the year. 但我希望它显示到年底为止的所有日期。
The completely dynamic approach would be a query based on generate_series()
: 完全动态的方法是基于generate_series()
的查询:
SELECT the_date::date
FROM generate_series('2013-01-01 0:0'::timestamp
, date_trunc('year', now()::timestamp)
+ interval '1 year - 1 day'
, interval '1 day') the_date;
Always use ISO 8601 format for dates and timestamps, which works irregardless of locale settings. 始终对日期和时间戳使用ISO 8601格式,无论区域设置如何,都可以使用。
A final cast to date
( the_date::date
), because the function returns timestamp
(when fed timestamp
arguments). 最终转换为date
( the_date::date
),因为该函数返回timestamp
(当输入timestamp
参数时)。
The expression 表达方式
date_trunc('year', now()::timestamp) + interval '1 year - 1 day'
calculates the last day of the current year. 计算当年的最后一天。 Alternatively you could use EXTRACT (year FROM now())::text || '-12-31')::date
或者,您可以使用EXTRACT (year FROM now())::text || '-12-31')::date
EXTRACT (year FROM now())::text || '-12-31')::date
, but that's slower. EXTRACT (year FROM now())::text || '-12-31')::date
,但速度较慢。
You can wrap this into a custom "table-function" (aka set-returning function ) that you can basically use as drop-in replacement for a table name in queries: 您可以将其包装到自定义的“表函数” (又名set-returning函数 )中,该表函数基本上可以用作查询中表名的替代品:
CREATE OR REPLACE FUNCTION f_dates_since_2013()
RETURNS SETOF date AS
$func$
SELECT the_date::date
FROM generate_series('2013-01-01 0:0'::timestamp
, date_trunc('year', now()::timestamp)
+ interval '1 year - 1 day'
, interval '1 day') the_date;
$func$ LANGUAGE sql STABLE;
Example: 例:
SELECT * FROM f_dates_since_2013();
Going one step further, you could create a table or - more elegantly - a MATERIALIZED VIEW
based on this function (or the underlying query directly): 再进一步,您可以基于此函数(或直接在基础查询中)创建一个表,或者-更优雅地-一个MATERIALIZED VIEW
:
CREATE MATERIALIZED VIEW my_dates(the_date) AS
SELECT * FROM f_dates_since_2013();
Call: 呼叫:
SELECT * FROM my_dates;
All you have to do now is to schedule a yearly cron job that runs REFRESH MATERIALIZED VIEW
at the start of each new year: 您现在要做的就是安排一个年度cron作业 ,该作业在每个新年开始时运行REFRESH MATERIALIZED VIEW
:
REFRESH MATERIALIZED VIEW my_dates;
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