获取一个Postgres数组的最后一个元素，以声明 [英] Getting the last element of a Postgres array, declaratively

问题描述

如何获取数组的最后一个元素Postgres的？

How to obtain the last element of the array in Postgres?

我需要做的声明，因为我想用它作为一个ORDER BY标准。我不想创建一个特殊的PGSQL功能吧，到数据库的变化较少在这种情况下，就更好了。

I need to do it declaratively as I want to use it as a ORDER BY criteria. I wouldn't want to create a special PGSQL function for it, the less changes to the database the better in this case.

其实，我想要做的是包含多个单词的特定列的最后一个字排序。改变模型不在这里一个选项。

In fact, what I want to do is to sort by the last word of a specific column containing multiple words. Changing the model is not an option here.

在换句话说，我要推Ruby的 sort_by {| X | x.split [-1]} 到数据库级别。我可以一个值分成的话阵列的Postgres string_to_array 或 regexp_split_to_array 功能，那么如何获得它的最后一个元素？

In other words, I want to push Ruby's sort_by {|x| x.split[-1]} into the database level. I can split a value into array of words with Postgres string_to_array or regexp_split_to_array functions, then how to get its last element?

推荐答案

如果我正确地理解你的问题，你有一个字符串，你是第一个分裂它的一些分离，然后再把找到数组的最后一个元素并丢弃其余部分。

If I understand your question correctly you have a string and you're first splitting it on some separator and then afterwards finding the last element of the array and discarding the rest.

您可能会错过中间人和直接拿到最后一个元素：

You could miss out the middle man and get the last element directly:

SELECT regexp_replace('foo bar baz', '^.* ', '')

结果：

baz

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