postgresql 通过添加月份来计算 Postgres 中的日期？
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Calculating a date in Postgres by adding months?
提问by Elitmiar
I have a postgres table that has the following fields
我有一个具有以下字段的 postgres 表
start_date,duration
开始日期，持续时间
duration contains any number of months, so to calculate the end date you add the months in duration to the start date. Now I want to do something like this with a postgres query.
持续时间包含任意数量的月份，因此要计算结束日期，请将持续时间中的月份添加到开始日期。现在我想用 postgres 查询做这样的事情。
SELECT *
FROM table
WHERE start_date > '2010-05-12'
AND (start_date + duration) < '2010-05-12'
Is this possible and how does one right the syntax?
这是可能的，如何正确使用语法？
The version of my postgres is PostgreSQL 8.1.22 on x86_64-redhat-linux-gnu, compiled by GCC gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)
我的postgres的版本是 PostgreSQL 8.1.22 on x86_64-redhat-linux-gnu，由GCC gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)编译
回答by manji
try:
尝试：
(start_date + (duration * '1 month'::INTERVAL)) < '2010-05-12'
or
或者
(start_date + (duration || ' month')::INTERVAL) < '2010-05-12'
More info: Date/Time Functions and Operators
更多信息：日期/时间函数和运算符
回答by Arj
You might find this article useful: PostgreSQL: month := interval '30 days';
您可能会发现这篇文章很有用：PostgreSQL: month := interval '30 days';
Also this link: http://wiki.postgresql.org/wiki/Working_with_Dates_and_Times_in_PostgreSQL, more specifically the section called "WORKING with DATETIME, DATE, and INTERVAL VALUES".
还有这个链接：http: //wiki.postgresql.org/wiki/Working_with_Dates_and_Times_in_PostgreSQL，更具体地说是名为“WORKING with DATETIME, DATE, and INTERVAL VALUES”的部分。
