Question

我有一张带有相关照片表的产品表，可以保存每周广告的产品，例如每年52套产品。我有一个单独的产品和照片库记录区域，使用触发器更新/插入，使库保持最新的产品/图像保存。

插入/更新效果很好。

我希望在删除产品图片时删除库图像，但仅当它不是因为产品级联删除时才会删除（如果他们删除了产品，我仍然希望将产品保留在库中。如果他们删除了一张单独的照片，我想从图书馆中删除该单张照片）

如何在照片表触发器中知道删除是否是级联的结果？我在插入/更新/删除后尝试检查缺失的产品记录，但就触发器而言，这些记录仍然存在。

create table product (
    id int not null -- primary key
)

create table productimage (
    id int not null -- primary key
    , parentid int not null -- foreign key to product id
)

alter trigger dbo.UpdateProductImageLibrary
on dbo.productimage 
after update, insert as
begin
    declare @insertedcount int, @deletedcount int
    select @deletedCount = count(*) from deleted
    select @insertedCount = count(*) from inserted

    declare @isInsert bit, @isUpdate bit, @isDelete bit

    if( @deletedCount = 0 and @insertedCount > 0)
    begin
        set @isInsert = 1; set @isUpdate = 0; set @isDelete = 0
    end
    if( @deletedCount > 0 and @insertedCount = 0)
    begin
        set @isInsert = 0; set @isUpdate = 0; set @isDelete = 1
    end
    if( @deletedCount > 0 and @insertedCount > 0)
    begin
        set @isInsert = 0; set @isUpdate = 1; set @isDelete = 0
    end

    -- At this point we know if product image is an insert, update or delete
    -- but the parent table's records are still there if we 
    -- check for them, even during a cascading delete
end

SQL Server触发器：如何知道父表记录何时被删除

0 个答案: