如何选择12个月以上的数据?

本文介绍了如何选择12个月以上的数据?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一张桌子，如下:

caravan_id, description, date_purchased, special_instructions, health&safety_check, notes

health&safety_check是日期字段.

如何对该表中的数据执行SQL查询，以返回health&safety_check早于12个月的所有行.但是，如果可能的话，则以12个月为基础，而不是以今天的日期为基础，例如< 2011年10月12日

How can I perform an SQL query for data in this table that returns all rows which have a health&safety_check older than 12 months. But if possible one that is based on 12 months, not on today's date such as < 10/12/2011

推荐答案

类似的东西

select * from t where add_months("health&safety_check", 12) < sysdate

我假设您不想硬编码当前日期，但很乐意为它使用变量.

I assume you don't want to hardcode the current date but are happy with using a variable for it.

Jeff在评论中提出了一个很好的观点(尽管在Oracle中，您可以在函数上创建索引，以便解决问题).这很容易解决:

Jeff, in the comments, makes a good point (although, in Oracle, you can create an index on a function so you can get around the problem). This is easily fixed:

where "health&safety_check" <add_months(sysdate, -12)