通过比较一组列值创建一个新列 [英] Create a new column by comparing set of column values

问题描述

如何根据表中的product_id"对一组行进行分组，并通过比较组内的一组列值来创建新列?

How can I group a set rows by 'product_id' from a table and create a new column by comparing a set of column values within the group ?

例如

product id   part_id  availability
1            1        true
1            2        false
1            3        true
2            1        true
2            4        true
2            8        true

通过比较可用性"，我想创建一个可行性"列.如果缺少单个零件，则不可行.

By comparing the 'availability',I would like to create a 'feasibility' column. If single part is missing it would't be feasible.

product_id  feasibility
1           false
2           true

我使用 GROUP BY 子句按 product_id 对它们进行排序，但我无法弄清楚第二部分.

I used GROUP BY clause to sort'em out by product_id but I can't figure out the second part.

推荐答案

如果您只对问题中显示的两列感兴趣，有一个非常简单的解决方案:

There is a very simple solution available, if you are only interested in the two columns shown in your question:

select product_id, min(availability) feasible
from tbl group by product_id

请看这里的小演示:.http://rextester.com/GMT80394

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