Question

我使用Microsoft SQL Server Management Studio在T-SQL中编写了一个触发器，在我发现一个漏洞之后，我缩小了触发器的范围。这使我的一个触发器停止工作，我无法弄清楚原因。

工作流应该是这样的：删除事件，通过EventId上的外键，删除EventEquipment。由于不再需要设备，因此应将NumberofEquipmentNeeded添加回名为EquipmentAvailabilities的表中设备的可用性。

以下是我的代码。我在插入工作时具有reduce可用性，并且在删除工作之后添加了可用性，直到我添加到仅执行该日期

create trigger trgAddNumberAvailable
on EventEquipments
after delete
as
begin

    declare @eventEquipmentId int;

    select @eventEquipmentId = EventEquipmentId
    from deleted;

    declare @eventId int;

    select @eventId = EventId
    from deleted;

    --selects the eventID from EventEquipment

    declare @eventDate date;

    select @eventDate = EventDate
    from Events 
    where Events.EventId = @eventId;
   --finds the date for the Event that was chosen above becuase EventEquipment does not contain date

    declare @equipmentId int;

    select @equipmentId = EquipmentId
    from deleted
    where deleted.EventEquipmentId = @eventEquipmentId;

    declare @numberRequested int;

    select @numberRequested = NumberOfEquipmentNeeded
    from deleted 
    where deleted.EventEquipmentId = @eventEquipmentId;

    update EquipmentAvailabilities
    set NumberAvailable = NumberAvailable + @numberRequested
    where EquipmentId = @equipmentId  
      and EquipmentAvailabilityDate = @eventDate;

    --will update the availability for the equipment from insert and the date it is
    --available that was chosen from the Event date from the event that was deleted

Answer 1

你使用了很多次选择..从删除只是为了填充变量。而是使用一个选择并填充所有变量。

另请注意替代查询。表之间的关系不明确。

create trigger trgAddNumberAvailable
on EventEquipments
after delete
as
begin

    declare @eventEquipmentId int;
    declare @eventId int; 
    declare @eventDate date;
    declare @equipmentId int;
    declare @numberRequested int;

    select @eventEquipmentId = EventEquipmentId, @eventId = EventId
    ,@equipmentId = EquipmentId,@numberRequested = NumberOfEquipmentNeeded
    from deleted;

     --selects the eventID from EventEquipment
      select @eventDate = EventDate
    from Events 
    where Events.EventId = @eventId;
   --finds the date for the Event that was chosen above becuase EventEquipment does not contain date

    update EquipmentAvailabilities
    set NumberAvailable = NumberAvailable + @numberRequested
    where EquipmentId = @equipmentId  
      and EquipmentAvailabilityDate = @eventDate;

    --will update the availability for the equipment from insert and the date it is
    --available that was chosen from the Event date from the event that was deleted

    --OR (alternative query for bulk delete ,(Correct the join))
    update EquipmentAvailabilities
    set NumberAvailable = NumberAvailable + @numberRequested
    from EquipmentAvailabilities EA
    inner join   deleted d
    on ea.EquipmentId = d.equipmentId  
    inner join Events E 
    on d.EventId=e.EventId
    where 
      ea.EquipmentAvailabilityDate = e.eventDate;

删除后触发在更改后不起作用

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