select   unnest(array['a','b'])   as index_code，  unnest(array[a,b]) as  index_value  from(select  a,  b,from 表 ) t

case when可以的

参考https://blog.csdn.net/wxfghy/article/details/86630435

array_to_string(ARRAY_AGG (text),',')

-----------------------------------------------------

------------------------------------------------------

SELECT

  frwybs,

  array_to_string(

    ARRAY_AGG (DISTINCT relative_label_content),

    ','

  ) as labels_content

FROM

  frk_s.label_cor_gene

GROUP BY

  frwybs

labels_content

------------

AA,BB,CC