mysql - 从 Mysql 中的连接结果中选择不同的值

Question

我试图从 mysql 中的两个表中访问完整数据，然后从结果集中找到列的不同值。尝试使用嵌套查询，如下所示:-

Select distinct s.BlockName 
from (SELECT * 
      FROM constucted
      LEFT JOIN required ON constucted.BlockName = required.BlockName 

      UNION

      SELECT * 
      FROM constucted
      RIGHT JOIN required ON constucted.BlockName = required.BlockName
     ) s

如 Stackoverflow Reference 中所述 并尝试使用 with 关键字如下:-

WITH CTE
AS
(
   SELECT * 
   FROM constucted
   LEFT JOIN required ON constucted.BlockName = required.BlockName

   UNION

   SELECT * 
   FROM constucted
   RIGHT JOIN required ON constucted.BlockName = required.BlockName
)
SELECT DISTINCT BlockName
FROM CTE

但无法为 BlockName 列找到不同的值，无法为其准备查询。

Answer 1

您的查询似乎更简单地写为:

select BlockName 
from constructed
union -- intentional to remove duplicates
select BlockName
from required;