在Oracle SQL中构造临时表

Question

我正在尝试创建一个"存储"两个值之间的解码的子表,因为我需要多次使用该解码.让我们说这些是我的表:

Table Person
Name    Number_name
Jeremy  One
Thomas  Two
Stephen Three

我当前的SQL看起来像这样:

SELECT
    decode (number_name,
    'one',1,
    'two',2,
    'three',3,
    'four',4)
    num
    FROM person where name = 'Jeremy'
    and (some other condition)
UNION SELECT
    decode (number_name,
    'one',1,
    'two',2,
    'three',3,
    'four,4)
    num
    FROM Person
    where Name <> "Jeremy"
    and (some other condition)

我希望能做的是这样的:

SELECT num from my_temp_table where name = "Jeremy" and (some other condition)
union select num from my_temp_table where name <> "Jeremy" and (some other condition)
...

其中my_temp_table是在该查询期间构造的(它在查询完成运行时不再存在)并且看起来像

Table my_temp_table
Name  num
One   1
Two   2
Three 3
Four  4

希望我能做到这一点,而不是"选择一个名字,1个来自双联盟的数字......"

这可行吗？

Answer 1

该WITH条款听起来与你所描述的最接近.但这需要您以某种方式生成数据.从中选择DUAL可能是最简单的选择

WITH my_temp_table AS (
  SELECT 'One' name, 1 num from dual union all
  SELECT 'Two', 2 from dual union all
  SELECT 'Three', 3 from dual union all
  SELECT 'Four', 4 from dual
)
SELECT *
  FROM my_temp_table 
       JOIN person ON (<<some join condition>>)
 WHERE <<some predicate>>

既然你不想结合大量的查询,你可以做类似的事情

WITH my_temp_table AS (
  select level num,
         initcap( to_char( to_date( level, 'J' ),
                           'JSP' )) name
    from dual
 connect by level <= 4
)
...