英文:
How can I find the last member of an array in PostgreSQL?
问题
如何在PostgreSQL中找到数组的最后一个成员？
例如，您有一个包含课程ID的数字数组，在您选择的课程列表中，我想知道最后一个课程的ID：[1,32,4,6]，我需要的是数字6！如何找到最后一个数字，也就是6？
英文:
How can I find the last member of an array in PostgreSQL?
for example you have an array of the numbers which each of them are id of a course, in the list of your chosen courses I want to know the last one : [1,32,4,6] I need number 6 ! how can I find the last number which is 6 ?
答案1
得分: 2
你可以使用array函数array_upper()来获取最后一个元素的索引。
考虑以下示例：
with t as (select '{1,32,4,6}'::int[] a)
select a[array_upper(a, 1)] last_element from t
| last_element |
| -----------: |
| 6 |
英文:
You can use array function array_upper() to get the index of the last element.
Consider:
with t as (select '{1,32,4,6}'::int[] a)
select a[array_upper(a, 1)] last_element from t
<pre>
| last_element |
|---|
| 6 |
| </pre> |
答案2
得分: 0
你可以使用ARRAY_UPPER来获取数组的上限。然后，您可以检索返回的索引处的值。
SELECT yourcolumn[ARRAY_UPPER(yourcolumn,1)] FROM yourtable;
英文:
You can use ARRAY_UPPER to get the upper bound of your array. You can then retrieve the value at that returned index.
SELECT yourcolumn[ARRAY_UPPER(yourcolumn,1)] FROM yourtable;
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