Question

以下查询将不起作用，但应该清楚我正在尝试做什么：在空间上拆分't'的值并使用子查询中该数组中的最后一个元素（因为它将匹配tl ）。任何想法如何做到这一点？谢谢！

SELECT t, y, "type",
regexp_split_to_array(t, ' ') as t_array, sum(dr), (

select uz from f.tfa where tl = t_array[-1]

)
as uz,
sc
FROM padres.yd_fld
WHERE y = 2010 AND pos <> 0
GROUP BY t, y, "type", sc;

Answer 1

我认为你不能在postgresql（文档）中引用数组元素的负面索引吗？

test=# select t from 
      (select regexp_split_to_array('hi man bye', ' ') as t) as x;       
--------------
 {hi,man,bye}
(1 row)

test=# select t[1] from 
      (select regexp_split_to_array('hi man bye', ' ') as t) as x;
 t
----
 hi
(1 row)

test=# select t[-1] from 
      (select regexp_split_to_array('hi man bye', ' ') as t) as x;
 t
---

(1 row)

我觉得奇怪的是它没有出错，但是......

正确的方法是：

test=# select t[array_length(t,1)] from 
  (select regexp_split_to_array('hi man bye', ' ') as t) as x;
  t
-----
 bye

另外，请看这里：

Getting the last word from a Postgres string, declaratively

postgres子查询w /派生列

1 个答案: