Question

到目前为止我发现的是

select ARRAY(
   select unnest(ARRAY[ 'a', 'b', 'c' ])
   except
   select unnest(ARRAY[ 'c', 'd', 'e' ])
)

我们可以这样做，只找到两个字符串数组之间的非匹配元素。

还有其他最好的办法吗？

与整数数组一样，我们可以这样做

SELECT int[1,2,3] - int[2,3]

Answer 1

select array_agg(e order by e)
from (
    select e
    from
    (
        select unnest(array[ 'a', 'b', 'c' ])
        union all
        select unnest(array[ 'c', 'd', 'e' ])
    ) u (e)
    group by e
    having count(*) = 1
) s

Answer 2

这是另一种选择：

select ARRAY
(
   (
     select unnest(ARRAY[ 'c', 'd', 'e' ])
     except
     select unnest(ARRAY[ 'a', 'b', 'c' ])
   )
   union 
   (
     select unnest(ARRAY[ 'a', 'b', 'c' ])
     except
     select unnest(ARRAY[ 'c', 'd', 'e' ])
   )
);

或者（为了更清楚地说明涉及两个不同的数组）：

with array_one (e) as (
   select unnest(ARRAY[ 'a', 'b', 'c' ])
), array_two (e) as (
   select unnest(ARRAY[ 'c', 'd', 'e' ])
)
select array(
   ( 
      select e from array_one
      except 
      select e from array_two
   )
   union 
   (
     select e from array_two
     except 
     select e from array_one
   )
) t;

如果元素的顺序很重要，则需要将array_agg（）用作Clodoaldo Neto（而不是使用array(...)构造函数）：

with array_one (e) as (
   select unnest(ARRAY[ 'a', 'b', 'c' ])
), array_two (e) as (
   select unnest(ARRAY[ 'c', 'd', 'e' ])
)
select array_agg(e order by e)
from (
   ( 
      select e from array_one
      except 
      select e from array_two
   )
   union 
   (
     select e from array_two
     except 
     select e from array_one
   )
) t;

在postgresql中只查找两个字符串数组之间的非匹配元素的最佳方法是什么

2 个答案: