Oracle 条件存储过程中的 WHERE

Question

我想为 select 载体编写一个存储过程，使用附加参数 'i_showEmptyCarrier' 来指定是否需要隐藏或显示空载体。

+---------------------------+
|          Carriers         |
+----+----------+-----------+
| id | label    | location  |
+----+----------+-----------+
| 1  | carrier1 | warehouse |
+----+----------+-----------+
| 2  | carrier2 | warehouse |
+----+----------+-----------+
| 3  | carrier3 | factory   |
+----+----------+-----------+

我需要查询 'products' table 以检查载体是否为空。

+-------------------------------------------+
|                  products                 |
+----+-----------+----------------+---------+
| id | carrierid | productiondate | deleted |
+----+-----------+----------------+---------+
| 1  | 1         | 09/09/2020     | 1       |
+----+-----------+----------------+---------+
| 2  | 1         | 09/09/2020     | 0       |
+----+-----------+----------------+---------+
| 3  | 1         | 09/09/2020     | 0       |
+----+-----------+----------------+---------+
| 4  | 2         | 10/09/2020     | 0       |
+----+-----------+----------------+---------+
| 5  | 2         | 10/09/2020     | 0       |
+----+-----------+----------------+---------+

所以在这种情况下，carrier3 是空的。
我想要的存储过程逻辑是：

PROCEDURE GetCarriers
(
    i_showEmptyCarrier IN number,
    c_Carriers OUT t_cursor
)
AS
BEGIN
OPEN c_Carriers FOR 
SELECT 
label,
(   select count(*) 
    from products 
    where products.carrierid = carriers.carrierid
    and records.deleted = 0
) as nrOfProducts
FROM carriers
if(i_showEmptyCarrier == 1) {
//select carriers without a product
WHERE nrOfProducts = 0 ;
}
else{
//select carriers with a product
WHERE nrOfProducts > 0 ;
}
END GetCarriers;

所以如果 'i_showEmptyCarrier' = 1，那么 3 号空载机将被 selected，

+----------+--------------+
| label    | nrOfProducts |
+----------+--------------+
| carrier3 | 0            |
+----------+--------------+

否则只有 1 号和 2 号运营商被 selected。

+----------+--------------+
| label    | nrOfProducts |
+----------+--------------+
| carrier1 | 2            |
+----------+--------------+
| carrier2 | 2            |
+----------+--------------+

Answer 1

看来您受到了很多 Java（或其他编程语言）的影响。我不确定你到底想要什么。但这里是你如何实现你想要的。

create or replace procedure p_get_carriers(pi_carrier_flag in varchar2, po_carriers out t_cursor)
is
    lt_cursor   t_cursor;
begin
    select  *
    bulk collect into lt_cursor
    from    records
    where   deleted = case when pi_carrier_flag = 'Y' then 0 else deleted end;
    po_carriers := lt_cursor;
exception
when others then
    po_carriers := null;
end p_get_carriers;

意味着您不需要 if-else 块来处理它。您可以在查询本身的 where 子句中执行此操作。

注意：我不知道您的 table 结构和集合细节。我猜它并发布代码。您可能需要相应地进行调整。

Answer 2

如何修改查询以使用 left join 和 conditional aggregation 最后比较输入，

SELECT label,nrOfProducts
FROM
(
  SELECT c.label,SUM(CASE WHEN p.deleted = 0 THEN 1 ELSE 0 END) nrOfProducts
   FROM carriers c
  LEFT JOIN products p 
  ON p.carrierid = c.id
  GROUP BY c.label
)
WHERE ((&i_showEmptyCarrier = 1 AND nrOfProducts = 0) 
       OR (&i_showEmptyCarrier = 0 AND nrOfProducts > 0));

您仍然可以使用 where 子句代替 if-else。

Answer 3

您希望在一种情况下使用内部联接而在另一种情况下使用外部联接。由于外连接仅意味着 outer-joined 行的所有列都为空，但是，在这两种情况下您都可以简单地进行外连接，然后才决定是关闭还是保留 outer-joined 行。

在 SQL 中，这很简单：

select *
from carriers c
left join products p on p.carrierid = c.id
where (:show_empty = 'only non-empty' and p.id is not null)
   or (:show_empty = 'only empty' and p.id is null)
   or (:show_empty = 'all')

（当然，您可以将其汇总为 count(p.id)。在这种情况下，您可以 group by c.id 或查看一个运营商 where c.id = :carrier_id。）

Oracle 条件存储过程中的 WHERE

Oracle conditional WHERE in stored procedure

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stored-procedures