影子说：

with cte_jx as (
select name, 'itemA' as item_key, itemA as item_value from t_jx
union all
select name, 'itemB' as item_key, itemB as item_value from t_jx
union all
select name, 'itemC' as item_key, itemC as item_value from t_jx)
select *
  from cte_jx
 where name ='Jhon'
   and item_value <> 0;

结果：

name|item_key|item_value|
----+--------+----------+
Jhon|itemB   |         1|
Jhon|itemC   |         1|

根据需要将行旋转回列。