Sql Oracle：如何使用明细表中的最新行更新master？_Sql_Oracle_Plsql_Oracle9i

Sql Oracle：如何使用明细表中的最新行更新master？

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Sql Oracle：如何使用明细表中的最新行更新master？,sql,oracle,plsql,oracle9i,Sql,Oracle,Plsql,Oracle9i,我们有两张桌子：车辆：身份证注册号 LastAllocationUserName 上次分配日期 LastAllocationId 分配：身份证车辆ID 用户名日期用最新分配更新车辆表中的每一行最有效（最简单）的方法是什么？在SQL Server中，我将使用“更新自”，并使用最新配置加入每辆车。Oracle没有来自的更新。你在甲骨文中是怎么做到的 **编辑** 我要求最好的SQL查询更新。我将使用触发器更新主表中的数据。我知道怎么写触发器。我要问的是如何编写SQL查询来更新V

我们有两张桌子：

车辆：

身份证
注册号
LastAllocationUserName
上次分配日期
LastAllocationId

分配：

身份证
车辆ID
用户名
日期

用最新分配更新车辆表中的每一行最有效（最简单）的方法是什么？在SQL Server中，我将使用“更新自”，并使用最新配置加入每辆车。Oracle没有来自的更新。你在甲骨文中是怎么做到的

**编辑**

我要求最好的SQL查询更新。我将使用触发器更新主表中的数据。我知道怎么写触发器。我要问的是如何编写SQL查询来更新Vehicle表。举个例子就好了。谢谢。

当前设置要求您使用分配表上的触发器来维护糟糕的决策选择。也就是说，使用：

UPDATE VEHICLE
   SET (LastAllocationUserName, LastAllocationDate, LastAllocationId) =
       (SELECT a.username,
               a.date,
               a.id
          FROM ALLOCATIONS a
          JOIN (SELECT b.vehicleid, 
                       MAX(b.date) AS max_date
                  FROM ALLOCATIONS b
              GROUP BY b.vehicleid) x ON x.vehicleid = a.vehicleid
                                     AND x.max_date = a.date
         WHERE a.vehicleid = VEHICLE.id)

从VEHICLE表中删除有问题的列，并使用视图提供最新的分配信息，这样做会更好。

当前设置要求您在分配表上使用触发器，以保持错误的决策选择。也就是说，使用：

UPDATE VEHICLE
   SET (LastAllocationUserName, LastAllocationDate, LastAllocationId) =
       (SELECT a.username,
               a.date,
               a.id
          FROM ALLOCATIONS a
          JOIN (SELECT b.vehicleid, 
                       MAX(b.date) AS max_date
                  FROM ALLOCATIONS b
              GROUP BY b.vehicleid) x ON x.vehicleid = a.vehicleid
                                     AND x.max_date = a.date
         WHERE a.vehicleid = VEHICLE.id)

从VEHICLE表中删除有问题的列，并使用视图提供最新的分配信息，可以更好地实现这一点。

在Oracle中使用另一个表“更新”的最简单方法是使用MERGE

MERGE INTO vehicle v
USING (
  -- subquery to get info you need
) s ON (v.id = s.vehicleId)
WHEN MATCHED THEN UPDATE SET 
  username = s.username 
  ...

在Oracle中使用另一个表“更新”的最简单方法是使用合并

MERGE INTO vehicle v
USING (
  -- subquery to get info you need
) s ON (v.id = s.vehicleId)
WHEN MATCHED THEN UPDATE SET 
  username = s.username 
  ...

从设计的角度来看，我更喜欢在车辆表上主动维护这三个字段，并将“分配”填充为历史记录表（可能通过触发器）。将父表上的更新下推到子表上的插入比另一种方式容易得多。

从设计的角度来看，我更喜欢在Vehicle表上主动维护这三个字段，并将“分配”填充为历史表（可能通过触发器）。将父表上的更新下推到子表上的插入比将父表上的更新下推到子表上的插入容易得多

UPDATE VEHICLE V
   SET (LastAllocationId, LastAllocationDate, LastAllocationUserName) =
   (SELECT a.id
           ,a.date
           ,a.username
      FROM ALLOCATIONS a
      where a.VehicleId = V.id
        and a.date = ( select max(Last_a.date) from ALLOCATIONS Last_a
                       where Last_a.VehicleId = V.id )
    )

你说得对。具有历史记录表的视图速度较慢。没有快速“加入最后一张唱片”这样的事情。触发器是最好的解决方案。如果可以，第一次使用PL填充。它更容易理解和维护

DECLARE
   Last_date DATE;
   Last_User Varchar2(100);
   Last_ID number;
Begin
FOR V IN ( Select * from VEHICLE )
LOOP
   select max(date) into Last_date 
   from ALLOCATIONS Last_a
   where Last_a.VehicleId = V.id;

   IF Last_date is NULL then 
      Last_User := NULL;
      Last_ID := NULL;
   else
      select Id,UserName into Last_id, Last_user
      from ALLOCATIONS Last_a
      where Last_a.VehicleId = V.id
      and Last_a.date = Last_date;
   END IF;

   UPDATE Vehicle 
     set LastAllocationUserName = Last_User
         ,LastAllocationDate = Last_date
         ,LastAllocationId Last_id
   Where id = V.id;

END LOOP;
End;

警告：此处写入，未测试

DECLARE
   Last_date DATE;
   Last_User Varchar2(100);
   Last_ID number;
Begin
FOR V IN ( Select * from VEHICLE )
LOOP
   select max(date) into Last_date 
   from ALLOCATIONS Last_a
   where Last_a.VehicleId = V.id;

   IF Last_date is NULL then 
      Last_User := NULL;
      Last_ID := NULL;
   else
      select Id,UserName into Last_id, Last_user
      from ALLOCATIONS Last_a
      where Last_a.VehicleId = V.id
      and Last_a.date = Last_date;
   END IF;

   UPDATE Vehicle 
     set LastAllocationUserName = Last_User
         ,LastAllocationDate = Last_date
         ,LastAllocationId Last_id
   Where id = V.id;

END LOOP;
End;

警告：此处写入，未测试。

是否在触发器内查找更新

CREATE TRIGGER ALLOCATION_I
AFTER INSERT ON ALLOCATION
REFERENCING NEW AS NEW
FOR EACH ROW
Begin

UPDATE Vehicle 
 set LastAllocationUserName = :NEW.Username 
 ,LastAllocationDate = :NEW.date 
 ,LastAllocationId = :NEW.id 
WHERE Id = :NEW.VehicleId;

END;

你在寻找触发器内部的更新吗

CREATE TRIGGER ALLOCATION_I
AFTER INSERT ON ALLOCATION
REFERENCING NEW AS NEW
FOR EACH ROW
Begin

UPDATE Vehicle 
 set LastAllocationUserName = :NEW.Username 
 ,LastAllocationDate = :NEW.date 
 ,LastAllocationId = :NEW.id 
WHERE Id = :NEW.VehicleId;

END;

正如大多数其他人所指出的：由于数据模型的原因，您有一个大问题。大多数为这个模型编写的代码，将比它需要的困难得多。我已经通过上下投票和一些评论说了这一点，但这还不够

如果您继续您的路径，那么下面的代码将演示需要执行的操作。希望它能吓到你：-）

示例表：

SQL> create table vehicles (id,registrationnumber,lastallocationusername,lastallocationdate,lastallocationid)
  2  as
  3  select 1, 1, 'Me', sysdate-1, 2 from dual union all
  4  select 2, 2, 'Me', sysdate, 3 from dual
  5  /

Table created.

SQL> create table allocations (id,vehicleid,username,mydate)
  2  as
  3  select 1, 1, 'Me', sysdate-2 from dual union all
  4  select 2, 1, 'Me', sysdate-1 from dual union all
  5  select 3, 2, 'Me', sysdate-1 from dual
  6  /

Table created.

触发器必须查看自己的表以确定最后的分配。Oracle通过引发变异表错误来防止此类脏读。为了避免这种情况，我创建了一个SQL类型和一个包：

SQL> create type t_vehicle_ids is table of number;
  2  /

Type created.

SQL> create package allocations_mutating_table
  2  as
  3    procedure reset_vehicleids;
  4    procedure store_vehicleid (p_vehicle_id in vehicles.id%type);
  5    procedure adjust_vehicle_last_allocation;
  6  end allocations_mutating_table;
  7  /

Package created.

SQL> create package body allocations_mutating_table
  2  as
  3    g_vehicle_ids t_vehicle_ids := t_vehicle_ids()
  4    ;
  5    procedure reset_vehicleids
  6    is
  7    begin
  8      g_vehicle_ids.delete;
  9    end reset_vehicleids
 10    ;
 11    procedure store_vehicleid (p_vehicle_id in vehicles.id%type)
 12    is
 13    begin
 14      g_vehicle_ids.extend;
 15      g_vehicle_ids(g_vehicle_ids.count) := p_vehicle_id;
 16    end store_vehicleid
 17    ;
 18    procedure adjust_vehicle_last_allocation
 19    is
 20    begin
 21      update vehicles v
 22         set ( v.lastallocationusername
 23             , v.lastallocationdate
 24             , v.lastallocationid
 25             ) =
 26             ( select max(a.username) keep (dense_rank last order by a.mydate)
 27                    , max(a.mydate)
 28                    , max(a.id) keep (dense_rank last order by a.mydate)
 29                 from allocations a
 30                where a.vehicleid = v.id
 31             )
 32       where v.id in (select column_value from table(cast(g_vehicle_ids as t_vehicle_ids)))
 33      ;
 34    end adjust_vehicle_last_allocation
 35    ;
 36  end allocations_mutating_table;
 37  /

Package body created.

然后，3个数据库触发器将更新代码从行级别移动到语句级别，从而避免了变异表错误：

SQL> create trigger allocations_bsiud
  2    before insert or update or delete on allocations
  3  begin
  4    allocations_mutating_table.reset_vehicleids;
  5  end;
  6  /

Trigger created.

SQL> create trigger allocations_ariud
  2    after insert or update or delete on allocations
  3    for each row
  4  begin
  5    allocations_mutating_table.store_vehicleid(nvl(:new.vehicleid,:old.vehicleid));
  6  end;
  7  /

Trigger created.

SQL> create trigger allocations_asiud
  2    after insert or update or delete on allocations
  3  begin
  4    allocations_mutating_table.adjust_vehicle_last_allocation;
  5  end;
  6  /

Trigger created.

还有一个小测试，以验证它是否在单用户环境中工作：

SQL> select * from vehicles
  2  /

        ID REGISTRATIONNUMBER LA LASTALLOCATIONDATE  LASTALLOCATIONID
---------- ------------------ -- ------------------- ----------------
         1                  1 Me 13-05-2010 14:03:43                2
         2                  2 Me 14-05-2010 14:03:43                3

2 rows selected.

SQL> insert into allocations values (4, 1, 'Me', sysdate)
  2  /

1 row created.

SQL> select * from vehicles
  2  /

        ID REGISTRATIONNUMBER LA LASTALLOCATIONDATE  LASTALLOCATIONID
---------- ------------------ -- ------------------- ----------------
         1                  1 Me 14-05-2010 14:03:43                4
         2                  2 Me 14-05-2010 14:03:43                3

2 rows selected.

SQL> update allocations
  2     set mydate = mydate - 2
  3   where id = 4
  4  /

1 row updated.

SQL> select * from vehicles
  2  /

        ID REGISTRATIONNUMBER LA LASTALLOCATIONDATE  LASTALLOCATIONID
---------- ------------------ -- ------------------- ----------------
         1                  1 Me 13-05-2010 14:03:43                2
         2                  2 Me 14-05-2010 14:03:43                3

2 rows selected.

SQL> delete allocations
  2   where id in (2,4)
  3  /

2 rows deleted.

SQL> select * from vehicles
  2  /

        ID REGISTRATIONNUMBER LA LASTALLOCATIONDATE  LASTALLOCATIONID
---------- ------------------ -- ------------------- ----------------
         1                  1 Me 12-05-2010 14:03:43                1
         2                  2 Me 14-05-2010 14:03:43                3

2 rows selected.

现在，您所要做的就是添加一些序列化，使其在多用户环境中100%工作。但希望这个例子足够可怕

问候,，

Rob.

正如大多数其他人所指出的：由于数据模型的原因，您遇到了一个大问题。大多数为这个模型编写的代码，将比它需要的困难得多。我已经通过上下投票和一些评论说了这一点，但这还不够