基于用户定义的 WHERE 子句

Question

我有一个变量，date_order，我在 SELECT 子句中定义，

rank() over (partition by a.mother order by to_char(a.from_date, 'dd-mm-yyyy') desc) as date_order.

我希望仅包含 date_order=1 的观察结果。

但是，如果我在下面的语句 and date_order=1 中将条件 date_order=1 包含到 WHERE 子句中，则会出现错误。我在这方面的问题是：

是否可以以 SELECT 子句中定义的 date_order 为条件？如果是，我该如何正确执行此操作？
如果不可能，你对我应该如何继续有什么建议吗？

我使用以下代码：

select to_char(a.from_date, 'dd-mm-yyyy') as fromdate, a.mother, a.mother_NAME,a.mother_GROUP, a.child_WEIGHT,
a.NODE_NO, a.NODE_NO_PARENT,
rank() over (partition by a.mother order by to_char(a.from_date, 'dd-mm-yyyy') desc) as date_order
,c.child_WEIGHT as PARENT_child_WEIGHT
from table_a a
left join table_b b
on a.mother_ref=b.mot_ref
left join table_c c
on a.NODE_NO_PARENT=c.NODE_NO and a.mother=c.mother
where 1=1
and a. NODE_TYPE in ('Model mother') 
and  a.child_WEIGHT <> 0
and  c.child_WEIGHT <> 0 
;

提前谢谢你。如果我使用 SQL 语法有误，请随时纠正我，但请记住，这只是我第三次使用 SQL.

此致，

Answer 1

将其放入某些 CTE（参见 https://docs.oracle.com/cd/E17952_01/mysql-8.0-en/with.html），然后您将能够针对 date_order 列进行过滤。

它可能看起来像这样：

WITH cte as
(
    select 
            to_char(a.from_date, 'dd-mm-yyyy') as fromdate, a.mother, a.mother_NAME,a.mother_GROUP, a.child_WEIGHT,
            a.NODE_NO, a.NODE_NO_PARENT,
            rank() over (partition by a.mother order by to_char(a.from_date, 'dd-mm-yyyy') desc) as date_order
            ,c.child_WEIGHT as PARENT_child_WEIGHT
    from table_a a
    left join table_b b on a.mother_ref=b.mot_ref
    left join table_c c on a.NODE_NO_PARENT=c.NODE_NO and a.mother=c.mother
    where 1=1
    and a. NODE_TYPE in ('Model mother') 
    and a.child_WEIGHT <> 0
    and c.child_WEIGHT <> 0 
)
select * from cte
where date_order = 1;

Answer 2

尝试使用 select 而不是 select。

select * from (
select to_char(a.from_date, 'dd-mm-yyyy') as fromdate, a.mother, a.mother_NAME,a.mother_GROUP, a.child_WEIGHT,
a.NODE_NO, a.NODE_NO_PARENT,
rank() over (partition by a.mother order by to_char(a.from_date, 'dd-mm-yyyy') desc) as date_order
,c.child_WEIGHT as PARENT_child_WEIGHT
from table_a a
left join table_b b
on a.mother_ref=b.mot_ref
left join table_c c
on a.NODE_NO_PARENT=c.NODE_NO and a.mother=c.mother
where 1=1
and a. NODE_TYPE in ('Model mother') 
and  a.child_WEIGHT <> 0
and  c.child_WEIGHT <> 0
)t
where t.date_order = 1

据我所知，您不能在同一 SELECT 语句

的 WHERE 块中使用别名（在您的情况下 date_order）

基于用户定义的 WHERE 子句

WHERE clause based on user-defined

sql

where-clause

oracle-sqldeveloper