从查询创建视图 - oracle

Posted 2023-02-26

【中文标题】从查询创建视图 - oracle

【英文标题】：Create view from query - oracle

【发布时间】：2019-01-31 19:12:50

【问题描述】：

我有在 oracle apex 中使用的查询。是否有可能从此查询中创建 jasper 报告的视图（Jasper 不支持 cte）。

注意：P99_DATE_FROM和P99_DATE_TO是参数！

with cte as (
SELECT
    a.name,
    w.order as order,
    s.num as num,
    w.id,
    (Select count(*) from quant where id = w.id and trunc(date) between :P99_DATE_FROM and :P99_DATE_TO) as QUANT
FROM
    web w
    left outer JOIN tabel_1 a ON a.id = w.id
    left outer JOIN tabel_2 s ON s.id = w.id
WHERE
    (trunc(s.date) between :P99_DATE_FROM and :P99_DATE_TO or :P99_DATE_FROM is null or :P99_DATE_TO is null)

)
    SELECT 
        name,
        SUM(order) as TOTAL,
        SUM(num) as NUM,
        QUANT
    from cte
    group by name,QUANT

【问题讨论】：

为什么不直接使用内联视图呢？

@AlexPoole 我不知道怎么用！

【参考方案1】：

您可以parameterize a view，但使用 Apex 提供的参数会使它（甚至）更加复杂。

由于您只在主查询中引用一次 CTE，因此使用内联视图会更简单，将您的 CTE 查询变成子查询：

SELECT 
    name,
    SUM(order) as TOTAL,
    SUM(num) as NUM,
    QUANT
from (
    SELECT
        a.name,
        w.order as order,
        s.num as num,
        w.id,
        (Select count(*) from quant where id = w.id and trunc(date) between :P99_DATE_FROM and :P99_DATE_TO) as QUANT
    FROM
        web w
        left outer JOIN tabel_1 a ON a.id = w.id
        left outer JOIN tabel_2 s ON s.id = w.id
    WHERE
        (trunc(s.date) between :P99_DATE_FROM and :P99_DATE_TO or :P99_DATE_FROM is null or :P99_DATE_TO is null)
)
group by name,QUANT

【参考方案2】：

WITH 子句的正常使用通过它的备用名称、子查询分解来揭示。当想要在我们的查询中多次使用子查询时，它们很方便，比如在两个whatever IN ( sub-query ) 过滤器中。

这不适用于您的情况，因此您可以简单地将 CTE 转换为内联视图：

SELECT 
    name,
    SUM(order) as TOTAL,
    SUM(num) as NUM,
    QUANT
from  (
    SELECT
        a.name,
        w.order as order,
        s.num as num,
        w.id,
        (Select count(*) 
         from quant 
         where id = w.id and trunc(date) between :P99_DATE_FROM and :P99_DATE_TO) as QUANT
    FROM
        web w
        left outer JOIN tabel_1 a ON a.id = w.id
        left outer JOIN tabel_2 s ON s.id = w.id
    WHERE
        (trunc(s.date) between :P99_DATE_FROM and :P99_DATE_TO
          or :P99_DATE_FROM is null or :P99_DATE_TO is null)
    ) cte
 group by name,QUANT