如何在同一列上连接来自同一表的不同条件的两个结果集？

Question

select * from unit_of_measure;
+--------+-----------+--------+------------+--------------+-----------------+-------------+---------------+------------------+
| uom_id | uom_name  | symbol | created_by | created_date | created_ip_addr | modified_by | modified_date | modified_ip_addr |
+--------+-----------+--------+------------+--------------+-----------------+-------------+---------------+------------------+
|      1 | number    | NULL   | NULL       | NULL         | NULL            | NULL        | NULL          | NULL             |
|      2 | kilograms | NULL   | NULL       | NULL         | NULL            | NULL        | NULL          | NULL             |
|      3 | liters    | NULL   | NULL       | NULL         | NULL            | NULL        | NULL          | NULL             |
+--------+-----------+--------+------------+--------------+-----------------+-------------+---------------+------------------+

从这张表中，我试图组合两个结果集，如：

select uom_name as uomname1 from unit_of_measure where uom_id=1;

select uom_name as uomname2 from unit_of_measure where uom_id=2;

谁能帮我加入这两个结果集。我曾尝试使用 union 但它没有解决问题。

Answer 1

试试他的代码：

  select u1.uom_name as uomname1 
    from unit_of_measure  as u1 inner join unit_of_measure  as u2
     on u1.uom_id=u2.uom_id
     where u1.uom_id=1 
    ans u2.uom_id;

但你可以得到相同的结果：

select uom_name from unit_of_measure where uom_id in (1,2);