如何在 WHERE 子句中使用 IF...ELSE 条件？

Question

我试图在我的 WHERE 子句中使用 IF...ELSE 构造来有选择地将条件应用于我的SELECT.

这应该工作吗？

CREATE OR REPLACE package body If_Else_Pack IS

    PROCEDURE Moving
    (
        obj_A       IN varchar2,
        obj_B       IN varchar2,
        obj_C       IN varchar2,
        obj_D       IN varchar2,
        cur_Result  OUT T_CURSOR
    ) IS
    BEGIN
        OPEN cur_Result FOR
        SELECT 
            w.assetid,
            w.vehiclenumber,
            w.LatLong,
            w.CurrentSpeed,
            w.timeOfMovement,
            w.CurrentPlace,
            w.curTime,
            w.motion,
            w.fuelR,
            w.VehicleStart
        FROM waypoints1 w
        WHERE 
            IF ((obj_D= '0' OR obj_D IS NULL) AND (obj_C= '0' OR  obj_C IS NULL)) THEN
                WHERE w.customer_id =obj_A
                AND w.delegate_user_id = obj_B;
            ELSE IF ((obj_D= '0 'OR obj_D IS NULL) AND (obj_C<> '0' OR obj_C IS NOT NULL)) THEN
                WHERE w.customer_id = obj_A
                AND w.category_id = obj_C
                AND w.delegate_user_id = obj_B;
            ELSE IF ((obj_D<> '0' OR obj_Dis NOT NULL) AND(obj_C= '0' OR obj_C IS NULL)) THEN
                WHERE w.customer_id = obj_A
                AND w.fleet_id = obj_D
                AND w.delegate_user_id = obj_B;
    END MOVING;
END IF_ELSE_PACK;

Answer 1

我认为这个问题有点误导并导致人们无法正确思考。看起来这 3 个条件不会重叠，所以您需要做的就是OR将 3 个语句放在一起：

create or replace package body If_Else_Pack is

  Procedure Moving(obj_A IN varchar2,
                   obj_B  IN varchar2,
                   obj_C IN varchar2,
                   obj_D    IN varchar2,
                   cur_Result     OUT T_CURSOR) is

   begin

        open cur_Result for
        select w.assetid,
                 w.vehiclenumber,
                 w.LatLong,
                 w.CurrentSpeed,
                 w.timeOfMovement,
                 w.CurrentPlace,
                 w.curTime,
                 w.motion,
                 w.fuelR,
                 w.VehicleStart
        from waypoints1 w
        where 
        (((obj_D= '0' or obj_D is null) and (obj_C= '0' oR  obj_C is null)) 
                 and w.customer_id =obj_A
                 and w.delegate_user_id = obj_B)
        or
        (((obj_D= '0 'or obj_D is null) and (obj_C<> '0' or obj_C is not null)) 
           and w.customer_id = obj_A 
           and w.category_id = obj_C 
           and w.delegate_user_id = obj_B)
        or
        (((obj_D<> '0' or obj_D is not null) and (obj_C= '0' or obj_C is null))
           and w.customer_id = obj_A
           and w.fleet_id = obj_D
           and w.delegate_user_id = obj_B);
END MOVING;
END IF_ELSE_PACK;

该WHERE条件可被进一步简化为：

        WHERE 
              w.customer_id = obj_A
          AND 
              w.delegate_user_id = obj_B
          AND 
              ( (obj_D = '0' or obj_D IS NULL) AND (obj_C= '0' OR obj_C IS NULL) 
             OR 
                (obj_D = '0' or obj_D IS NULL) AND (w.category_id = obj_C) 
             OR 
                (w.fleet_id = obj_D) AND (obj_C= '0' OR obj_C IS NULL) 
              ) ;

Answer 2

您应该查找CASE 结构。阿德里安的文章很有帮助。Oracle 文档位于此处。

对于您想要执行的查询类型，我不禁认为数据库模式中存在一些遗漏。您当然可以在 obj_C 和 obj_D 上添加一些约束，以便不允许使用 null 吗？这会让事情变得简单。