根据参数显示列

Question

我正在尝试编写 SQL 脚本来显示基于用户参数的列。我无法在任何地方找到可接受的答案。

这是我想做的事情的简化版本（在 OracleDB 中）：

SELECT Table_car.purchase_date  AS PurchaseDate,
       Table_car.sale_date AS SaleDate,
       CASE WHEN :userinput <> 999 THEN (SELECT Table_car.car_brand FROM Table_car WHERE Table_car.car_brand = :userinput ) 
       ELSE (SELECT Table_car.car_brand FROM Table_car) 
       END AS CarBrand

FROM Table_car

我想要的伪代码可以是

if(user_input = 999)
   show_all_values_of(Table_car.car_brand );
else
   show_only_some_values_of(Table_car.car_brand, user_input);

这是预期的结果：

if user_input <> 999 (if is 1, for example)
| PurchaseDate | SaleDate   | CarBrand |
+--------------+------------+----------+
|  03/12/2018  | 09/10/2021 |    1     |
----------------------------------------
|  13/06/2011  | 20/11/2021 |    1     |
----------------------------------------
|  22/01/2020  | 09/12/2021 |    1     |
----------------------------------------

else (if user input is 999)
| PurchaseDate | SaleDate   | CarBrand |
+--------------+------------+----------+
|  03/12/2018  | 09/10/2021 |    1     |
----------------------------------------
|  13/06/2001  | 20/11/2021 |    5     |
----------------------------------------
|  22/01/2020  | 09/12/2021 |    1     |
----------------------------------------
|  03/12/2018  | 09/10/2021 |    3     |
----------------------------------------
|  13/06/2012  | 10/10/2020 |    9     |
----------------------------------------
|  22/01/2020  | 09/12/2020 |    2     |
----------------------------------------

Answer 1

您可以将逻辑放入 where 子句中，使用 or；类似于：

SELECT Table_car.purchase_date AS PurchaseDate,
       Table_car.sale_date AS SaleDate,
       Table_car.car_brand AS CarBrand
FROM   Table_car
WHERE  :userinput = 999 OR Table_car.car_brand = :userinput

如果您的列可以为空，您可能需要额外的逻辑以特定方式处理它，但看起来不应该如此。如果您需要 where 中的其他条件，请记住在上面的逻辑周围加上括号，以确保它按照您的意图进行解释；即

WHERE  (:userinput = 999 OR Table_car.car_brand = :userinput)
AND ... something else

顺便说一句，您可能需要考虑使用 table 别名来减少输入。

根据参数显示列

Show column according to parameter

sql

oracle

oracle-sqldeveloper