在字符SQL中拆分字符串

Question

如何在字符中拆分字符串并在PostgreSQL中的每个字符后添加一个新行

例如

num  desc
 1    Hello
 2    Bye

num  desc
 1    H
      e
      l
      l
      o

 2    B
      y 
      e

Answer 1

select num, regexp_split_to_table(descr,'')
from the_table
order by num;

SQLFiddle：http://sqlfiddle.com/#!15/13c00/4

然而，角色的顺序并不能保证，并且实现这一点有点复杂。

以Erwin's answer regarding this problem：

为基础

select case 
         when row_number() over (partition by id order by rn) = 1 then id 
         else null
       end as id_display, 
       ch_arr[rn]
from (
  select *, 
         generate_subscripts(ch_arr, 1) AS rn
  from (
    select id, 
           regexp_split_to_array(descr,'') as ch_arr
    from data
  ) t1
) t2
order by id, rn;

修改

如果您只想为每个id分配一个字符串，其中字符由换行符分隔，您可以使用：

select id, 
       array_to_string(regexp_split_to_array(descr,''), chr(10))
from data
order by id