Oracle SQL 合并/连接不起作用（并排）

Question

谁能解释为什么这没有产生预期的结果？

select a.*, b.Feb22 
from (
    select 
        'Wtd Avg FICO' as Metric
        ,750.5 as Jan22
    from dual
    union all
    select 
        'Wtd Avg DTI' as Metric
        ,0.35 as Jan22
    from dual
    union all
    select 
        'Wtd Avg LTV' as Metric
        ,0.75 as Jan22
    from dual
    ) a
inner join
select * 
from (
    select 
        'Wtd Avg FICO' as Metric
        ,700.5 as Feb22
    from dual
    union all
    select 
        'Wtd Avg DTI' as Metric
        ,0.50 as Feb22
    from dual
    union all
    select 
        'Wtd Avg LTV' as Metric
        ,0.25 as Feb22
    from dual
    ) b on a.Metric = b.Metric

期望的结果：

公制	1月22日	2月22日
Wtd 平均 FICO	750.5	700.5
重量平均 DTI	0.35	0.75
Wtd 平均 LTV	0.75	0.50

Answer 1

JOIN 只在两个表之间有效，你 b 不是一个我 sql 你需要重写它

在此处查看示例 db<>fiddle

select a.*, b.Feb22 
from (
    select 
        'Wtd Avg FICO' as Metric
        ,750.5 as Jan22
    from dual
    union all
    select 
        'Wtd Avg DTI' as Metric
        ,0.35 as Jan22
    from dual
    union all
    select 
        'Wtd Avg LTV' as Metric
        ,0.75 as Jan22
    from dual
    ) a
inner join
(select * 
from (
    select 
        'Wtd Avg FICO' as Metric
        ,700.5 as Feb22
    from dual
    union all
    select 
        'Wtd Avg DTI' as Metric
        ,0.50 as Feb22
    from dual
    union all
    select 
        'Wtd Avg LTV' as Metric
        ,0.25 as Feb22
    from dual
    ) b1 ) b on a.Metric = b.Metric

Answer 2

查询未能执行，因为在INNER JOIN之后没有指定表。

内部联接正在查找格式为INNER JOIN <table_name>的表，但您使用的是 SELECT 语句。

您可以通过在另一个子查询中嵌套 SELECT 语句来使用内联视图来解决此问题，如示例中所示。

SELECT a.*, b.Feb22 
  FROM (
        SELECT 'Wtd Avg FICO' as Metric
              ,750.5 as Jan22
          FROM dual
         UNION ALL
        SELECT 'Wtd Avg DTI' as Metric
              ,0.35 as Jan22
          FROM dual
         UNION ALL
        SELECT 'Wtd Avg LTV' as Metric
              ,0.75 as Jan22
          FROM dual
       ) a
 INNER JOIN (
SELECT * 
  FROM (
        SELECT 'Wtd Avg FICO' as Metric
              ,700.5 as Feb22
          FROM dual
         UNION ALL
        SELECT 'Wtd Avg DTI' as Metric
              ,0.50 as Feb22
          FROM dual
         UNION ALL
        SELECT 'Wtd Avg LTV' as Metric
              ,0.25 as Feb22
          FROM dual
        ) b_subquery
        ) b 
    ON a.Metric = b.Metric