是阵列中的所有PostgreSQL的空值 [英] Is array all NULLs in PostgreSQL

问题描述

时，如果有一个PostgreSQL阵列中的所有元素都为空返回TRUE一个前pression？

Is there an expression that returns TRUE if all the elements of a PostgreSQL array are NULL?

如果这是一个值NULL以外，当然我可以使用类似：

If it was a value other than NULL, I could of course use something like:

SELECT 4 = ALL (ARRAY[4,5]::integer[]);

不过，我想要做的所有操作与 IS NULL 测试，而不是一个 = 4 测试。我不认为有一个这样的所有的语法，并围绕NULL的语义与阵列，我不是我自己能想实现它的一种形式复杂。因此，我要求堆栈溢出。 ; - ）

However I want to do the ALL operation with an IS NULL test, rather than a = 4 test. I don't think there's an ALL syntax for this, and the semantics around NULL are compounded with arrays I've not myself been able to think of a form that achieves it. Hence my asking Stack Overflow. ;-)

我知道我可以写在PL / SQL函数或PL / pgSQL里做这个，但我想看看是否有诉诸之前直接EX pression。

I know I could write a function in pl/sql or pl/pgsql that does this, but I'd like to see if there's a direct expression before resorting to that.

推荐答案

我觉得我得到了最简单的回答，但仍preserving 4 = ALL（ARRAY [4,5] ::整数[]）; 构造：

I think I got the shortest answer, while still preserving 4 = ALL (ARRAY[4,5]::integer[]); construct:

select
y, true = ALL (select unnest(z) is null)
from x

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