通过引用引用表将数据移动到其他表时替换列的值

Question

假设我有一个名为“Table1”的表，其列和值如下

---------------------------
action | component | type |
---------------------------
  1    |     2    |  1    |
  2    |     3    |  3    |
  3    |     4    |  2    |
---------------------------

并且“Table2”与“table1”具有完全相同的结构。

现在我有另一个表“参考”，如下所示

---------------------------
description | id  | value  |
---------------------------
   action   |  2  |  create|
   action   |  1  |  delete|
   action   |  3  |  update|
  component |  2  |  c1    |
  component |  4  |  c2    |
  component |  3  |  c3    |
   type     |  2  |  t1    |
   type     |  1  |  t2    |
   type     |  3  |  t3    |
---------------------------

现在，我需要通过引用“reference”表中的值将数据从“table1”移动到“table2”。我的结果表应如下所示。

---

action | component | type |
---------------------------
delete |     c1    |  t2  |
create |     c3    |  t3  |
update |     c2    |  t1  |
---------------------------

请帮助我进行相同的查询。提前致谢。

Answer 1

您正在寻找多个连接：

select t1a.value as action,
       t1c.value as component,
       t1t.value as type
from table2 t2 join
     table1 t1a
     on t2.action = t1a.id and t1a.description = 'action' join
     table1 t1c
     on t2.component = t1c.id and t1c.description = 'component' join
     table1 t1t
     on t2.type = t1t.id and t1t.description = 'type';

Answer 2

你可以这样做：

select 
    (select b.description from reference b where A.action = b.id and b.description = 'action') as action,
    (select c.description from reference c where A.action = c.id and c.description = 'component') as component,
    (select d.description from reference d where A.action = d.id and d.description = 'type') as type
from table_1 A