将列移到行

Question

我需要在第一列中添加第三列（我希望第一列还将包括第三列）

当前状态：

所需结果：

Answer 1

您想要UNION ALL：

SELECT t.entity, t.activity
FROM table t
UNION ALL
SELECT t.entity2, t.activity2
FROM table t;

Answer 2

如果您有大量数据，则可能不想多次扫描表-union all就是这样做。

相反：

select (case when n.n = 1 then entity
             when n.n = 2 then entity_2
        end) as entity,
       (case when n.n = 1 then activity
             when n.n = 2 then activity_2
        end) as activity
from t cross join
     (select 1 as n from dual union all
      select 2 as n from dual
     ) n;

在Oracle 12C +中，使用横向联接可简化此操作：

select t.entity, s.activity
from t cross join lateral
     (select t.entity, t.activity from dual union all
      select t.entity_2, t.activity_2 from dual 
     ) s;

Answer 3

select entity, activity from <table>
union all
select entity_2, activity_2 from <table>

Answer 4

通常：

get_queryset