英文:
Postgresql - subtracting current year from integer field to populate a calculated field
问题
I have been working on this for longer than I care to admit. I am needing to subtract an integer field (ex. 1960) from the current year (as an int) and have the results put into a calculated field. I have worked out the following select statement which does return the correct answer.
当将选择语句添加为“始终生成”，则会引发以下错误。
subtracting two integers into a calculated field should be fairly simple...and I am lost as to why this is not working....
英文:
Using PostgreSQL 12. I have been working on this for longer than I care to admit. I am needing to subtract an integer field (ex. 1960) from the current year (as an int) and have the results put into a calculated field. I have worked out the following select statement which does return the correct answer.
.
When adding the select statement as a 'generate always' the following error is thrown.
subtracting two integers into a calculated field should be fairly simple...and I am lost as to why this is not working....
答案1
得分: 0
PostgreSQL目前仅实现了存储 生成列（不可变），而不是虚拟（可变，根据您的特定情况需要），考虑到虚拟生成列在读取时计算，而虚拟生成列类似于视图。
那么，您可以像这样将您的计算列实现为视图：
create view amp.amp_pumpstations_vw as
select *,
date_part('year', current_date)- inservice as asset_age
from amp.amp_pumpstations ap;
英文:
Since PostgreSQL currently implements only stored generated columns (immutable) and not virtual (mutable, as needed for your particular case), considering that a virtual generated column is computed when it is read and also a virtual generated column is similar to a view.
Then you could implement your calculated column as a view like this:
create view amp.amp_pumpstations_vw as
select *,
date_part('year', current_date)- inservice as asset_age
from amp.amp_pumpstations ap;
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